If the bard is trying to steal something from you in your sleep, generally as I would do as a DM, it would first have to make a stealthy throwing challenged by your passive perception to see it. he can approach your character without waking up. their. This would then be followed by a sleight of hand for the actual flight. Sleight of hand is listed on page 177 of the player's manual as a check used to
"Lift someone's wallet or slip something from his
by doing the skill that best fits the situation you describe. The difficulty depends on your DM, but usually the thresholds defined by the player's manual page 174 is:
- Very easy – DC 5
- Easy – DC 10
- Average – DC 15
- Hard – DC 20
- Very difficult – DC 25
- Almost impossible – DC 30
Factors that affect your DM's decisions must include the size, weight and noise of the object when moved.
However, I would like to know what you think as a player that your property is stolen by another player. This is a general convention (at least at my table and many of the questions I see on this site and others about my guy's syndrome, for example, this speech is a little long, but it summarizes some of the problems that the parties can resolve (cause) that stealing from other players can create an uncomfortable feeling within the party. It may be interesting to talk to the player or your DM about how this will affect the dynamics at the table before this happens.