Sure there is. There has to be a Googler here with the necessary access and can just mediate with their support department, run a few "select * from mails" quer

Sure there is. There has to be a Googler here with the necessary access and can just mediate with their support department, run a few "select * from mails" queries on their DB and use good judgement when asking the user to give info about the emails they know they have or have received. Heck, there should be some sort of PM/PO/Manager from Google here that should use this as a catalyst to have some sort of feature be built to solve this problem in some sort of risk-based approach.