My parents entered into an agreement of sale on their home on 5/28 with the fully executed contracts delivered on 5/29 at 3:30pm. Our attorney reviewed the contract on 6/3 and amended the contract to include a clause that the sellers must be able to coordinate the closings on both their existing home and new home which they entered into a contract on 6/2. The sellers (my parents) received the amendment at 4:30pm on 6/3 but the buyers copy had just been mailed. The buyer and agent arrived for home inspection at 6:00pm on 6/3 and I mentioned the amendment to the agent. She wanted to see it and when I showed our copy to her she stated "absolutely not. that the buyer had insisted from the beginning that their was to be no contingencies." I tried to make the agent understand that our attorney only wanted to make sure that both our buyer and the seller on the other home knew that both closings had to occur on the same day. She still held her ground and went to speak to her buyer alone and the home inpsection was stopped. My father was upset, the buyer was upset and every time I tried to reason with the buyer. I explained that both my parents are in their late 70's and in failing health and that our attorney was trying to make things as easy as possible to eliminate any undo stress. But it fell on deaf ears. At 9am on 6/4 I notified our attorney to rescind the amendment. He faxed a letter to the agent at 11:30am advising that we had rescinded the amendment. Our attorney was out of the office all afternoon. When our agent contacted the buyers agent at 5:30pm the agent stated that she had faxed a letter to my attorney at 12:30pm stating that the buyer was cancelling and was requesting deposit returned. The big question is can the buyer (who had not received a copy of the amendment nor did his agent, remember the agent only viewed my copy and never showed it to the buyer) cancel after the seller rescinded the amendment?

Yes. Even though you claim to have rescinded something they never saw, they had specified no contigencies. Your attorney goofed by changing the contract and gave them an out.

Yes, once you made that change, it became a counter offer, and they have the right to refuse that counter offer. After that you made a new offer ( same original offer by resending the change) but they have the right to not accept since your attorney making a change was in fact a counter offer.

If your attorney had not made that change you could have held them to the contract.