I don't think Ancestry has a problem with matches going back to any particular date. I think the wipe was based on things like cM/Mb size and whether the match was in a known "pile-up zone." Do you know where those 1728 matches were located (chromosome and position)? Perhaps it's a known problem area.

If you have the URL saved or use Snavely's tool, what happens when you try to visit the match page for your former 94% match? Perhaps they were downgraded. Most of my tests saw a healthy chunk of 2nd-4th cousins downgraded. If they aren't in your matches anywhere now, do you know where you match them (segment-wise)? Non-subscribers should still show up as matches.