The keeper, who is flying back to the UK to join Hull City on loan, had no chance with Alcardo van Graan's clever flick from a corner but felt it was important that the Reds responded moments later.
"The first half was obviously much quieter," he told MUTV. "We had a lot of the ball but it was all in the middle of the park and we didn't create much in the first half which we were disappointed about. When the lads grew more tired in the second half, they had more opportunities.
"I had a lot to do with my feet and a couple of saves but obviously it's little things in pre-season that happen. Judging distances and things like that. People talk about match fitness and match fitness for a keeper is about getting your distances and decision-making right, things like that. There were a couple of things like that but I was happy on the whole.
"We'd have been massively disappointed to lose. We're disappointed with a draw anyway with the amount of possession we had. To lose would have been very disappointing. Obviously, we want to get into the winning spirit and mentality so it's good we didn't lose the game."
Amos is looking forward to his move to Hull. "I can't wait," he enthused. "It's a new challenge and one I'm going to throw myself into and get as many games as I can. Then I'll come back here and look to push on."
Sir Alex has explained his thoughts on the loan transfer to the Championship side, soon after the keeper signed a new three-year contract at Old Trafford.