Possible Continuity Goof?

When Ashley and Jade get back to Ashley’s house after killing Sarah, I thought Ashley took the knife, bundle of bloody clothes, and boots, stuffed them in a box, then drove somewhere and dumped the whole thing in a dumpster.

Later, we see Ashley’s mom see Ashley washing her bloody boots in the sink. And later still, we see Ashley take that box of bloody clothes, get the knife and plant the knife in Jade’s house. So, what was it Ashley dumped in the dumpster then, if it wasn’t the original evidence?

BTW, I knew as soon as she had Jade “hold” the knife, Jade would get dinged with having her fingerprints on the knife. Of course, the cops later only mentioned that the blood on the knife was Sarah’s, no mention of the fingerprints.