I didn't see exactly what you were talking about s
Post# of 85468
A lot of trading software, especially the more advanced platforms that retail never gets to see, will allow the trader to direct their order(s) to the MM of their choice. Like if you were bidding .0301, and someone wanted it to print .03, they could direct their order into a .03 bid and bypass whatever bid is ahead.
Another reason could be because the trader on the other end put their order through another MM. Like if your bid was on NITE and the contra specified CDEL, your order will get bypassed.
Also, if your order was small enough that it didn't display, it could get put aside while larger blocks trade the next level. When that happens to me, I cancel replace the order, because in those instances I have no idea why my order is not printing.