Obviously there is no excuse for rudeness...
Although there may be a reason for it.
OP states the FA was doing the sales cart thing and yet that was no impediment to asking about the ETA. Which
a) the FA likely had no way of knowing
b) OP could have figured it out as mentioned above
c) could have waited until she wasn't busy.
If the FA had bitten her tongue with something along the lines of "I dont know Sir, the captain will no doubt update us when he knows" would OP still have been miffed ?
Cool Important Guy asks 'stewardess' question and is rebuffed. Hope the travelling companion was sufficiently impressed
.