No idea what the item is you are trying to buy but obviously one sounding in great demand.
A seller can cancel orders, though without the buyers permission, they do pay penalties , seller fees, and gain damaging defects on their account.
The cancellation citing out of stock would have the above sanctions imposed. The other reason excludes the penalties. So, there you can if you wish contact eBay CS explain you did not agree to cancel your item, a seller fee will be imposed as will the defect.
