The Mile High find came from an ex Topps Duryea employee's home and I don't believe there were any wrappers or checklists associated with it. I do think the checklists were packaged with the sprues, or at least some of them.
I bought an AL checklist at the AC National over a decade ago. I brought it to SGC to get graded and when I came back they said it could not be holdered; not because it was sheet cut but because it had an odd factory cut and they could not cut a gasket for it:
You can see how the top curves off to the right on both sides. The grader thought it was the result of high speed cutting.
I would think that in addition to those inserted into packs and those that were sheet cut, some would have been cut and left at the factory when the test fizzled and found their way to Card Collectors Co or Bill Haber eventually. Leftover sheets could even have been cut at the factory for the third party reseller.
Combined PSA/SGC pops are 49 checklists graded, of which 19 have number grades and the rest are Auth. There is only one high grade checklist, an SGC 96 NL. 21 AL and 28 NL have been graded overall.