How long does a merchant have to post a debit-card transaction? Must I keep funds available indefinitely?

I recently purchased an item with my debit card but have not yet seen record of the transaction. A friend of mine purchased an item with a similar card from the same vendor and saw a post to her account immediately. I realize a transaction can take a few days to clear but how long am I required to wait? Is there a time period in which merchants have to submit transactions or not? Similarly, if I write a check that is never cashed, is someone allowed to cash that check years later or is there legal protection for consumers?
There is no record at all on my online statement of a merchant request: no hold, no pending transaction, nothing… this is why I’m curious.

As soon as you purchase the item, the merchant sends an authorization request. Your card issuer will put a “hold” on the funds immediately. When the merchants sends through the clearing draft – anywhere between 1 and 5 days, usually, the amounts will be debited from your account and posted to the merchants account. Because of the “hold”, the bank will decline any transaction that exceeds your “open to buy”. That being the amount in your checking account, AFTER “holds” are deducted.
-MM

Edited – the ethical thing would be to call the merchant and find out why they didn’t put it through.
-MM

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