If I am testing a new food, or experimenting, or worried about my starting level, I test at an hour and then half hourly after that until I am satisfied I have dropped back to normal. The 2 hour thing, to me, is irrelevant. It is only a general guideline. In fact, the NICE guidelines changed last year. It now says "under 8.5 at least 90 minutes " after a meal, rather than 2 hours. 2 hours just isn't mentioned. This implies any time after 90 minutes, which sounds rubbish advice to me and means nothing, other than don't worry if you are higher than 8.5 during the first 90 minutes.
The fat content of a meal will impact on timings of subsequent BS rises, as will what you do between finishing the meal and testing. I doubt you sat still for 3 or 4 hours. Maybe a cup of tea/coffee? Although a sudden rise of 3mmol/l seems a lot. Could that have been a meter/strip/user error? Did you re-test it? I would have washed my hands again and re-tested.