When you give a gift, you should do it because you want to. It really shouldn't matter what happens next. I think it is better that you do not give a gift at all if you are going to have conditions in order to be satisfied with your gift giving.
Besides that, in a wedding situation, they are usually paying more for you to attend then the price of the gift that you bring, especially if you chose the toaster. Add to that, the fact that this is supposed to be your friend who is going thru plenty enough and took a huge financial loss or just waisted her families money, the last thing she or he needs to hear is that you want your gift back.