M.T.
I would have her use the bathroom before leaving school, you don't know how long it's been since she's gone and maybe she's dying to go on the way home and doesn't make it to the bathroom when you get there. If the accident isn't immediate, then perhaps it is an attention getter. What do you and she do right after daycare? Do you come home and do something with her right away like sit down and have snack, or read a story? If you are coming home and getting busy with other things, I'd shift into a pattern of spending 15 or 20 minutes with her as soon as you get home, despite all the other things calling for your attention, and see if this pattern changes.