How do we get paid for clients that disappear?

Twice now this has happened me, and I emailed support with the required info and they don't respond

I get a lead and both times the lead sheet said PAID on it, which I can only assume means they prepaid for this job

I get done with the job and send a payment request, and they don't answer messages or phone

What is the amount of time that the system waits after I select job done before that money the client prepaid is transferred to me?

What does thumbtack do to ensure we get paid from clients who use the service one time and leave before paying at the end of the job?

If the client prepaid and the job gets done, I am sure they just assume the money will go the pro, so if they ghost the platform and don't respond at all, where does that prepaid money go? it most certainly hasn't gone to me, the pro who did the work.