When items are restricted to some countries, you don't see the results when looking in your local ebay search result for the worldwide offers.
I could still see those offers if I log in the foreign ebay, in this example I would log into ebay.com rather than ebay.nl or ebay.fr.
Normally when in ebay.nl when I do 'worldwide' offers, I see everything sold in netherlands and everything sold elsewhere but shipped worldwide. If something is sold in USA but no shipped worldwide, I will only see the offer if I log into ebay.com.
Once you log in , you can aalways ask the vendor to allow selling to you (I have done thise often). But you need to have seen the offer before (if no autorisation from the vendor I will not be able to bid) and get a confirmation.
If I go look everyday what is on ebay, I don't specifically log everyday in 4 different versions of ebay, to be sure to see everything unfortunately (not enought ime and too much apita)
