My guess is that the mites are stressing him out which is why he is roaming. Also, did he eat the mouse or was he too startled? If he did NOT eat then he may be hunting. Idk how he managed the trick with the hide so he is good and sneaky lol maybe a little magic . I can easily assume that you are treating the mites so I'm not too worried about that. Leave him alone for a few days unless it's mite treatement and basic care stuff like water changes; if he is stressed a lot of handeling and disturbances will only stress him more.

I am also VERY glad that you found him so quickly! I would have been panicking if one of my two got out even for twenty min. I would be having a major cardiac arrest on the spot!