There is no way to add to an already made ability check
Any feature that adds to an ability check will include some phrase such as "the next ability check the creature makes" or "when a creature makes an ability check" or something similar because these bonuses are added when the check is actually made, not afterwards.
The rules on ability checks state:
[...] To make an ability check, roll a d20 and add the relevant ability modifier. [...]
When the d20 is rolled, the check is made; after that point, the check has already been made and things cannot modify it unless they explicitly state that they can modify already-made checks.
Stealth in particular states:
[...] Make a Dexterity (Stealth) check when you attempt to conceal yourself from enemies [...]
[...] When you try to hide, make a Dexterity (Stealth) check. Until you are discovered or you stop hiding, that check's total is contested by the Wisdom (Perception) check of any creature that actively searches for signs of your presence. [...]
None of this suggests that you can add to the check after it is made; the modifiers are applied when it is made and if you want to apply later modifiers then another check (a separate check) must be made.
The guidance spell is perhaps an odd case as it's worded as follows:
[...] Once before the spell ends, the target can roll a d4 and add the number rolled to one ability check of its choice. It can roll the die before or after making the ability check. [...]
I, personally, wouldn't interpret this as being able to apply to checks made in the past. I don't have any proof that the intent of the spell is to add to a check when it is made, but if they had intended for it to be added at a different time, I feel it would have been worded more carefully and much more clearly.
Furthermore, the part of the description that might imply retroactive uses of guidance is "before or after" in which case we can use guidance after the check or before it. I honestly have no idea what adding 1d4 to a check you haven't even made would do and would use this as evidence to support my case that guidance can't be applied retroactively.
The "before or after" bit is meant to allow somebody to choose whether they want to add the d4 after seeing their roll and the result of that roll. Compare it with the Battle Master Fighter's Precision Attack Maneuver:
When you make a weapon attack roll against a creature, you can expend one superiority die to add it to the roll. You can use this maneuver before or after making the attack roll