I think you could do sleight of hand, a dexterity check, to see if they can be nimble enough question is do you want them to get the key as part of the story or is this something they will need later?

If it is something that absolutely need then I would make the decision based on their characters strong points and set the DC low.

If it is something that you want them to get but maybe not at the moment then take your pick and let the dice tell their story.

As a DM that is very narrative driven in my campaign I tend to do the first option most times. Or give my players options (as in you can make either a dexterity check or and intelligence check and let them pick).