What happens if you drive a car in second gear at high speed for quite some distance?

I have a new Honda with little less than 1200 miles on it. Today while driving the car I put the gear in S (2) and drove at speed of 50+ mph for around 6-7 miles.
I felt something off about the car as the RPM was between 3500 to 4000 r/min while usually it is between 1500 to 2000 r/min. Also the engine sound was not it usual quite sound that comes - I thought because of the cold weather maybe it was sounding louder.
It was after stopping at a couple of red lights that I noticed that gear was at S(2)
I am quite paranoid about my car and mode of transportation.
Could someone let me know what are the effects of my driving?

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