I was specifically looking for this scenario out here, as my current situation is relative.
My wife and I made an offer and the seller accepted. We LOVE this house!! The purchase contract is signed, sealed, and delivered. I have all the necessary wheels in motion. I'm 99.9% certain my loan WILL get processed as my credit score is great. I have no contingencies and we own our current home free and clear.
However backing up a little, the property had a "Pending - Still Show" a month prior with a different potential buyer. Apparently the contract fell through. I noticed it came back online and available, so we jumped on it. I'm not exactly sure why, but my realtor speculates that it may have fell through on the appraisal, (the appraisal came back lower than the agreed selling price, perhaps). My guess is that the potential buyer didn't have the funds to make up that difference.
Hopefully I don't run into this same scenario with appraisal, but it's possible. Fortunately though I've taken out a Home Equity line of credit for a substantial amount so I'll have that cushion if I need it.
Anyway my advice would be that if it's a house you really really like and it's "Pending - Still Show", check on it everyday, because you just never know! Also, don't count on the listing agent to call you if the house comes back on the market because they didn't for me.
One last thing, apparently there are some other agents that are quite ticked off at the listing agent that they weren't notified either, and also the original buyers are mad because they apparently put a statement on their contract to the seller that they would agree to split the difference in the price gap of appraisal vs. agreed selling price, and they're trying to claim that the seller was not made aware of this. Not only that, I heard they had about $1,000 invested in inspections, (I'd be upset too).
On the other hand, I say too bad because that's your job along with the buyer's and seller's agents jobs to make sure everyone reads and understands everything in the contract including it's contingencies, stipulations, and counter-offers, etc.
Yay for us though :-)