The 19-year-old was thrown in for his Hornets debut against Leeds at the end of last season after first-choice Manuel Almunia was injured in the warm-up and back-up Jonathan Bond had to come off in the first half.
But Bonham's one and only Watford appearance ended in disappointment as he was at fault for both Leeds goals in a 2-1 defeat which ended their automatic promotion hopes.
The rookie keeper has since joined Brentford and suffered a case of deja vu on Tuesday night when Bees number one Simon Moore came off injured early in the first half of the friendly against Millwall.
But this time Bonham was up to the task, keeping a clean sheet and making some fine saves as the League One side ran out comfortable 3-0 winners.
"It happened on my debut at Watford now it's happened again," he said.
"I was due to go on at some stage but it was sprung on me again when Simon went down.
"But I feel confident now, I've learned you have to go in with confidence and not let it faze you.
"It was a steep learning curve at Watford. But now I've had games where I've had to step in. At Watford I didn't play much so I was nervous going into the Leeds game - but here I felt fine."