So i lost my htc desire last night ( . What is required for mobile phone insurance..do the insurers contact my provider and get details of the phone?
If you have insurance on the phone, here's what you need to do:

Suspend service on the phone immediately.
On the cell provider's website, look for a link to the insurance company.
Click the link and fill out the requested info.
During the process of filling out the info, it will ask for the type of phone you had.
Select that phone. If they can provide you with an exact replacement, they will.
You may get a suitable substitute, if they cannot provide the exact model.

Good luck!