Am I aware of the location of my Mage Hand, which I can't see, if it is obstructed as I move it?

Question

This is a follow up to my previous question about mage hand: Does the Mage Hand cantrip pass through solid surfaces?

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Last session, my Arcane Trickster was faced with some murky water and we needed to know how deep the bottom was. I decided to use mage hand to try to locate the bottom of the water without putting my own hand in there. We ruled that it wouldn't pass through the floor (which happily matches the conclusion of my previous question), but that raised the next question: do I know where it is?

The related question Do you need to be able to see the Mage Hand to use it? shows that you can move the mage hand without being able to see it, so not being able to see my mage hand once it had entered the water is not an issue (also, as an Arcane Trickster, it's invisible anyway).

Ordinarily, you know where your mage hand is because you explicitly move it, even if it's invisible, so if it starts in front of me as I cast it, and I move it 15 feet up, I know it is 15 feet above me because I moved it there; it can't be anywhere else, so I don't need to have any "locational feedback" from it in normal usage.

However, what about if the mage hand was not able to move to where I directed it to? If I moved it directly down by 30 ft, would I know (if, say, the water was 20 ft deep) that my mage hand only made it 20 ft and then stopped? Or would I be none the wiser to its exact location? Does the fact that I'm the caster make me somehow aware of its exact location, even if I can't see it, if something prevents it from moving as far as I directed it to?

Answer 1

You are an Arcane Trickster, this significantly alters the Mage Hand spell for you

First off, there is an important limitation to all uses of Mage Hand:

[...] The hand vanishes if it is ever more than 30 feet away from you or if you cast this spell again.

While, in your specific example, this limitation wouldn't trigger, in the case the moat or river was more than 30ft deep, you would know because the Mage Hand would cease to be something you can control.

In addition to this, the regular Mage Hand spell states:

[...]

You can use your action to control the hand. You can use the hand to manipulate an object, open an unlocked door or container, stow or retrieve an item from an open container, or pour the contents out of a vial. You can move the hand up to 30 feet each time you use it.

[...]

Being able to stow or retrieve items from containers safely, or in general to perform any sort of manipulation of objects, requires sensory feedback from the object itself (otherwise you would risk crushing the object, or smashing a potion vial into the side of the container).

So, one could easily make the case that the regular Mage Hand spell must provide some sensory feedback to the caster, due to the types of actions you can perform with the hand.

If that wasn't enough, you are an Arcane Trickster and the feature Mage Hand Legerdemain significantly alters what you can do with the hand:

Starting at 3rd level, when you cast mage hand, you can make the spectral hand invisible, and you can perform the following additional tasks with it:

• You can stow one object the hand is holding in a container worn or carried by another creature.

• You can retrieve an object in a container worn or carried by another creature.

• You can use thieves’ tools to pick locks and disarm traps at range.

You can perform one of these tasks without being noticed by a creature if you succeed on a Dexterity (Sleight of Hand) check contested by the creature’s Wisdom (Perception) check.

In addition, you can use the bonus action granted by your Cunning Action to control the hand.

Without knowing precisely where your Mage Hand is located, and getting sensory feedback from it, doing something, like lifting an object worn by another creature would be impossible. However the rules text of the feature specifically requires you to succeed on a Dexterity (Sleight of Hand) check using your characters skill in Sleight of Hand, not their spellcasting ability, while manipulating an invisible Mage Hand.

Sleight of Hand is specifically described as:

Whenever you attempt an act of legerdemain or manual trickery, such as planting something on someone else or concealing an object on your person, make a Dexterity (Sleight of Hand) check. The DM might also call for a Dexterity (Sleight of Hand) check to determine whether you can lift a coin purse off another person or slip something out of another person's pocket.

All of these examples require sensory feedback to successfully pull off.

As a result, for Arcane Trickster's at least, they know specifically and precisely where their Mage Hand is, and must get sensory feedback from it.

Answer 2

Nothing in the spell description suggests you know when your mage hand touches an object. Nor does it suggest you know its location.

You'll have to work with the GM to improvise a way for this to work as you're going off book.