Find my iphone

Hello and thanks for giving me an help.

In August someone have stolen my iphone 5 in Ibiza.

I immediately activated find my iphone and I locked it with a code and a message andated I madecided a complaint to police.

Today after 2 month find my iphone found it.

I also saw exactly the address.

The problem is that in minus than 2 minutes the device disappeared from my icloud and now I can't see it.

Someone can give me an help.

I have been in an Apple store but they say that it's strange and they cannot do nothing.