Bdsheets,
There have been some horses (probably a longer list than the one below) that ran sub-6 figs as a 2yo but never made it to the Derby (e.g., Macho Uno). Unfortunately, I don't have that list.
I do have a list such horses that did actually make it into the Derby over the last 7 years: Afternoon Delights (5.25 as 2yo), Halory Hunter (6), Favorite Trick (5.75), Artax (6), Excellent Meeting (5), High Yield (5), More Than Ready (4.25), Captain Steve (3.75), AP Valentine (5.5), Songandaprayer (6), Express Tour (5) and Point Given (3.5).
As you inferred, certainly not enough data to make a strong case but enough to make you wonder. Some of these horses may have had other strong factors (pace and breeding) to explain their poor performances. However, it is a fact that no horse has yet run a 6 or lower fig as a 2yo and managed to hit the board in the Derby. The trend in recent years has been toward more of these fast 2yos but such horses have yet to make an impact on the first Saturday in May.
Good luck to all.
Chris
