As the assuming bank after a failure, what is the escheatment process for accounts held at the failing bank? Is there something documented that I can reference?

Any assistance would be appreciated. Thank you.

The rules are going to be be set by the regional FDIC office. In general, property not claimed after within 18 months of the acquisition will be escheatable to the FDIC - not the state. The FDIC will handle escheating to the state at a later date. Contact the FDIC region that handled the case and find out what their specific guidance is.