Dont give up, even if it means looking through all those cases, but dont overlook the obvious spots. THe flour trick is good to! I dont know where u live but i look for the nnearest heat sorce if it is cold where u are. And with this i have no clue if it would work but if it is cold gett some hand warmer packets and put them in socks around various places in ur basement, and check them every once and a while and espically at night. Maby ull see him around, but if u have a generally warm basement i dont know if that would work the same. Good luck and I hope u find ur friend soon!