Yes, it's easy to rehydrate too-dry bud, and it's also easy to cause mold. Anything wet, like citrus, lettuce, etc. will make the air in the container humid, but you must not let it touch the bud. And you need to remove it in 12-24 hours and reseal the bud without the wet stuff. You could use a small piece of bread. The best way is to just add some fresh leaf, and that can mingle with your bud without worry.
Try some things, just keep a close eye on it.