We use to have 4 hamsters (one was a black bear like your!), our dwarf use to get out ALOT!!! One time she was gone for about a week, had given up on her...we had 2 cats too. Then one night I was watching CSI and out of the corner of my eye I saw movement...it was her, well after about a hour of chasing her (under couch, love seat, entertainment center & trying to keep the cats away (put them in the bathroom )finally I got her...covered in cobwebs hair a mess she looked like she ran threw a haunted house during a tornado!!! Anyway my point is sometimes it takes time but they do show up!
Good luck,
Gin
Good luck,
Gin