Anytime high humidity or slight rain or mist will start the rotors to rust.
Anytime the car sits for awhile.
If you drive and the rotors get cleaned off.
Then I would say no problem.
As for prior owner. 59K is more than enough to wear out the pads totally. Once worn, the driver would be having to stomp on the brakes hard to stop, heating up the rotors way more.
So IMO not to worry. If you current brakes are good (aside from the common surface rust) good to go.
No other permanent damge is caused by totally worn out brakes. So replacing the pads and rotors should be fine.
Also the calipers may have had some (red) dust on them, and it got into the pads and onto the calipers.
I really would not be worried.
If you are worried. Buy some 'brake clean' and taking the wheels off. spray the calipers and rotors. (the only problem with this is do not spray the caliper pin area .. the grease on them is needed!!)