Can someone else open my stolen iPhone and access my data?

3 days ago my iPhone was stolen. I am abroad now. The phone was bought from Turkey but I am in Poland and my device was stolen while in Poland. First I opened "activation lock" via Find my iPhone. I then pressed "erase device". I still have IMEI and serial number. Can anything be done with these numbers? I removed it from trusted devices and this phone is no longer among my devices on iCloud. The device is offline since it was stolen, I can only see an approximate location via "find my iphone". Can someone else open the device and access my data?

[Re-Titled by Moderator]