Jazzy as Lisa suggests contact Support. If you can verify the sale I bet they will help.
Also are you aware of the
http://refer.sitesell.com page. It lets you enter up to 100 of your "prospects." If they buy during the next 90 days you will get the commission (of course this is assuming they don't already have someone else's permanent cookie).
But to try and answer your larger question. Yes it never seems fair when someone else gets a commission that you feel you deserve. But without knowing the actual click path your prospect followed it's very hard to know exactly what they did before buying. Often they may not know themselves.
In the long run though I think you will win many that you don't necessarily deserve too. I think it all comes out in the wash. It may not sound fair but the cookie does cut both ways. Perhaps Lisa can share if that's the way she feels.
At any rate we do our best to come up with tools to help you "close the sale" especially if you have an offline prospect. Besides the refer.sitesell.com page we also have a Remote Order Form that lets you place an order directly for your customer. I don't think there is ANY other program that offers anything like that. Please tell if you know of any.
Also it's a great idea to offer an incentive to your "intimate" prospects to make sure they come back to you. An e-book or an hour's worth of help can go along way to "lock-in" that prospect to you... but only if they verify that they used your links or let you place the order for them.
At any rate definitely contact Support Jazzy. They definitely want to be fair if they can.
All the best,