Your friend's signature shows that cold medicine and anti-inflammatory drugs have been bitten. No one knows whether he ate them or not. To say the least, even if he has eaten, it's nothing. We often say that mice experiment, because mice and people have the most similar genetic constitution, so it is not surprising that mice eat those, otherwise they may not know where they fell from.

It is impossible for a mouse to enter a completely closed space, because it is not closed enough, and the mouse gets in through the gap. The mouse's bones are very few and very small, so it can drill through a gap smaller than its body, as shown in the picture.