Let's say you have two accounts at ComputerShare with DRSed GME stock. One of the accounts is in pure Book form while the other is mostly Book but also has a few in Plan. If you had the opportunity to see your entry in the ledger, then you could confirm whether or not the ledger showed you as having exactly 1000, 500, or something in between. Anything less than 1000 would support the Heat Lamp Theory.
Another thing worth doing is just summing all the non-DTC/Cede entries in the ledger to the extent possible in the time allowed, to confirm that they add up to whatever the DRS total is for that day. I would expect that would only be possible if the ledger does not list all of the shares in Plan accounts under their respective household investor names.