Can't say I have ever had this happen with a butt plug. It has happened with anal beads and a dildo, but the shape of a plug makes it hard. If anything, they can be a bit tricky to remove!
For me none would stay in until I got the XL plug ,normal look but it’s 3”diameter.sucker stays in to the point I can forget about it coming out. for a plug I think length should be as short as possible, decent size neck ,nice taper but a fairly aggressive drop off, and a oblong base ,round is uncomfortable for me .