Toyota Yaris 2012 ~115K km

My car is well taken care of, I bring it for maintenance 1x a year, I was the second owner and bought it at 27K km, never had an issue until...

2 days ago my car had a flashing engine light, would not accelerate past 40km and was shaking a little while idle.

I regrettably drove my car approx 10mins (5-6km) at ~30km an hour to the Toyota dealership for a diagnosis, and this morning the mechanic started up my car and was unable to reproduce the misfire. Diagnosis report said there was a misfire on cylinder 1, and because it wasn't actively misfiring they did the following to pinpoint the cause:

swapped cylinder 1 spark plug with cylinder 3

swapped cylinder 1 coil pack with cylinder 2

I was advised to monitor and bring it back it the problem arises again.

Side note: I was reading something about cold-start misfires, so I could let you guys know that it was about -25 degrees, but my car has started and run just fine on colder days (#Canada)

Questions:

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1. is it possible that it was a "one off" situation?

2. I know, no one can predict the future, but generally speaking how long should I wait before I'm in the clear?

3. how likely is it for this issue to arise again?

Thank you all so much!

Reposted for more feedback, I posted late last night and only got a few responses.