If they can show you that your account was logged into from some IP address that has nothing to do with you or where you have been then I would think you do not have to follow thru with the sales.

Ask ebay about that while on the phone to them.

If you don't follow thru you are likely to have some unhappy customers on your hands as mentioned above.

So given that you could be up for some NEGs or defects at least.

Try explaining to the buyers what has happened and guage if they are understanding or not.