Well, it certainly qualified as an awkward moment
I see three points:
1) The neighbors had not been neighborly enough to offer to pay in the past.
2) Mr X may be shy about knocking on the door of every house on the lane, thinking, don't these people know this costs money?
3) When he asked if you would collect, and you answered, 'we were thinking of getting you a card'. May have prompted the response about putting the snow back.
It could just be crossed wires, you thought he was doing it to be neighborly, in his own mind, he was being neighborly but began to think the privilege was getting abused.
I have helped neighbors with snow and never asked, wanted or took anything for it, it was always offered however - which I would consider polite. That he is your neighbor and has a big tractor, doesn't obligate him to clear your lane to be good neighbor IMO.
Decent neighbors are rare enough. If you like him well enough in other ways, don't make a big issue out of it. Just explain, like others have suggested, how it seemed to you and how it has to be in the future.
How do you and your neighbors go about shared lane maintenance the rest of the year?
Dave.