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'm quite paranoid about my car and mode of transportation.
Could someone let me know what are the effects of my driving?

You'll burn out 2nd gear.

You can cause extreme engine and transmission damage.

You wasted a bit of gas, that's all.

the engine can run all day at 4,000 rpm and suffer no harm, and the transmission was under no great stress from doing this either.

But pay more attention to your driving and instruments, they put them there for a reason, to let you know you left the car in the wrong gear.

This is another one of those "whatever damage you did, is already done" type questions. It should be OK though.