If you need something urgently, mail order (and any online purchase is really mail order) is not the way to go.
For urgent needs, buy locally, even if you pay a bit more. Time is money and money is time. (Seventeen cents a minute at minimum wage in Ontario.)
If your need is less urgent, but you want to be sure of your purchase, don't bid in an auction. There can be up to a ten day delay between your bid and the closing of the auction, with most bidding happening in the last few minutes. Then the seller has up to seven days to ship after your payment. Further, if you don't back your Paypal account with a credit card, your payment (e-cheque) may take up to ten days to clear the US and Canadian banking systems. And then it might spend 15 to 20 days in the postal system.
So an auction bid could take upwards of 47 days if everything goes badly before you have your item.
Only 'bid' on Fixed Price items if you want it immediately. Back your Paypal account with a credit card, which is an instant payment and also gives you a second level of Buyer Protection.
But, to answer your original question, most sellers only communicate with the winner of their items unless you have a specific question which in any case should be asked BEFORE bidding.
