Was there ever a comprehensive d20 or GMG list somewhere that might have this information?
Nothing that I recall doing, but you may want to check with the guys at the Acaeum. There are some collectors there who kept tabs on these things.
Don't put too much stock in those cover images. I have to solicit books 4-6 months out to meet distributor timelines. When I changed the logo way back when, this meant I had about 4-6 months worth of cover images
with the old logo already "out there" in the distributor catalogs. Then those books got printed
with the new logo. I think this happened around the time of DCC #15 or #16. This has come up before - people looking for those modules with the old cover logo - but they were never printed that way.