At the point counting was shut down election analysts would have known an educated guess of the final Trump vote total. These are the people determine when to call a state based on their analysis of historical precinct patterns.
So if the data at the time of stoppage is analyzed as it would have been on election night, based on the current total and yet to be counted precincts, you could approximate Trump's projected vote total. If the numbers for the Biden surge are the same it should show show the steal took place.
I've seen a lot of studies showing Biden over-performed in Trump districts. Just match that to a predicted Trump total at the time of stoppage.