4x4 on highway :(
 

I bought a Ford Ranger today as my first car/truck. On the way home, I drove with the 4x4 on the highway not knowing at the time it could cause driveshaft and transfer case damage (stupid me). It was raining, top speed around 65, little turning, distance: 60 miles and I made it home ok. Should I get it checked out/inspected? How much should I worry? Any input is appreciated...

It is not recommend but people do drive that way, so you will be fine.
And if you have PVH(pulse vacuum hubs, 1998-2000) then they probably were not engaged anyway.
If you need 4WD then these need to be changed to Rugged Ridge manual hubs, you can't rely on PVH hubs to work when you need them.

The Borg Warner 1354e transfer case(what a '99 Ranger has) doesn't have a way to allow both drive lines to spin at different speeds like All Wheel Drive transfer cases do(a clutch or viscous coupling).
But if your tires are all the same size it won't stress the transfer case that much.

If you think about it, when there is snow on the ground and you were in 4WD and the axles did spin at different speed you would be sliding all over the place, because wheels would be turning at different speeds.
That doesn't happen, well hopefully, so don't stress about it.

Sometimes you do need to back up to get transfer case and PVH hubs back into 2WD, after driving in 4WD for any distance, dry or on snow

Keep an eye on the system, if you have problems you might have done damage.

I dunno if once it reached the top allowable speed that the system would convert back to 2wd. The 4wd light might have clashed or even turned off indicating 2wd.

Thanks for the help.

You may have problems if it was done on a dry road but in the rain the surface is more slippery and should not stress the transfer case. When it is raining, I slip it into 4WD a lot of times when taking out from a stop to make sure I don't get wheel spin. I usually put it back into 2WD once I get up to speed or have to make a turn. If the turn is not sharp, I sometime leave it in 4WD if I want to accelerate, to maintain better traction in slippery conditions.

I used to do that all the time.

Play with your trans for any slip or something unusual.