Do Lycanthropes have immunity in their humanoid form?

Question

I once made a encounter featuring a human that was in fact a humanoid, as the encounter went. I had him flee from a surprise round in order to get a better position from the players. But during that scene, the human was shot by one of the heroes in the back. And with the humanoid having immunity from physical damage, I made it so that the wound was instantly healed after the hit (dealing 0 damage to the human).

Later throughout the encounter he transformed into his werewolf form and fought against the heroes. But sadly it was a fast fight for me (the DM), and he found himself beaten. (The heroes had magical items and/or a way to attack in a magical manner.)

He was then healed (1 hitpoint) in order to talk to the players. At the end of the interrogations, one of the players chose to knock him out (not kill him) by punching him in the face… And I said that he gave him a good swing of his fist and hit him hard in the face, which turned out to be effectless (due to his immunity).

Now here is my question… Was this stupid of my part? Do Were-creatures only have their immunity powers in their hybrid- and wolf form? (I mean, I think it was funny somehow.)

I remember reading into the book about this, but I couldn't find anything specific.

(I believe that the beginning of the encounter made for a very interesting start by showing that a human had [for some reasons] regenerative powers, but in the end of the encounter it was used as a joke.)

Answer 1

Werewolves have all their immunities in every form.

Its statistics, other than its AC, are the same in each form. (MM p.211, "Werewolf," at "Shapechanger")

Answer 2

If we're going by RAW, then yes, nothing in the monster manual specifies that damage immunities are conditional.

However I would point out that that would conflict with the idea of the curse if we consider characters who do not embrace the curse.

From MM 206 " By resisting the curse, a lycanthrope retains it's normal alignment and personality while in humanoid form. It lives it's life as it always has, burying deep the bestial urges raging inside it". Even though no mention of immunities or stat bumps are made, I highly doubt that turning into the Terminator while resisting a powerful curse means you live your life like nothing has happened.

On a side note I find that the Moonbeam spell, which forces the Shapechangers out of their forms is much more satisfying if it didn't just limit the attack options of Lycanthropes.