One player at my table is currently in a pretty specific situation, where he has a magic item inside his body. I have looked at the Detect Magic spell, and at the internet but I did not find anything on that specific situation (which is, admittedly, pretty unlikely). The detect magic states the following :
For the duration, you sense the presence of magic within 30 feet of you. If you sense magic in this way, you can use your action to see a faint aura around any visible creature or object in the area that bears magic, and you learn its school of magic, if any. The spell can penetrate most barriers, but it is blocked by 1 foot of stone, 1 inch of common metal, a thin sheet of lead, or 3 feet of wood or dirt.
So we have clear limitations for the case where the item is inside a lead or steel box, but I couldn't find anything about being inside of somebody or some creature. Is there any ruling or such that states how it works if the magic item to detect is inside of something ?