I had a trade (0044815) which failed before step one with no posted tx. I opened a support ticket which the arbitrator (my4t3kedin7k63a6) agreed and closed the ticket but the offer was not removed. I now can not reopen a ticket with Ctrl O as the ticket for this trade has already been opened and closed before.
You cannot delete this failed trade from inside the application ?
No, the trade failed after it was accepted, can not delete past this point
I guess the safest option would be to just leave it there, since there is no harm in it.
You can however switch to a new data directory if you wish. But that might be too much effort just for this. It is your choice though 