Wow thats a nice story lol. One of my friends had lost his cat when we were much younger and the cat simply came back about 6 months later and we were all very very surprised.

But a tarrantula reapearing after 3 months is even more surprising . The funny thing is he probably simply hid somewhere to molt and all that time he was still in your house without no one noticing him lol. I wonder what he's been eating though. A T. can certainly sustain for at least a month without food but 3 months is a very long time . I guess the fact that you leave the back door open allowed food to come inside the house lol.
I'm still pretty sure he enjoyed the first roach you gave him . Probably been a while since he's had such a good meal .

thx for sharing that story

Have a nice day

Krawll