You seem to have answered your own question.
If you were unwilling to complete the sale because it didn't reach the item you hoped for, the fault is entitrely yours. The feedback the buyer left for you is not removable.
The "false positive" feedback you left for the buyer is, if they report you to eBay for feedback policy violation.
Next time, you need to start the item at the lowest price you would be willing to accept.
