Grinding in the wheel.

It’s the classic problem. I just bought a 2018 SR5. Drove off the lot and checked into our hotel since we drove very far to get it. As we were driving through town and pretty heavy rain we began to hear a high pitched metal grinding sound as we moved. Some issues with it are
-it happened suddenly and continued until the drive was over and we parked.
-it makes the grinding sound when we move, not when we are braking.
-I can tell the sound is coming from the front drivers wheel. So something in that area is grinding.
-sound pitch change is proportional to speed(faster we go, higher the pitch)
-sound is only heard when we have the wheel straight, not so much when turning.
We parked and I decided to keep investigating. I went back out and started driving around the roads around my hotel. Nothing. The sound is gone. Now this since the sound is gone. I think 3 things. Wheel bearing, but there is none of the other symptoms of bad bearings(vibration, pulling, etc.) shim, or possibly some debris, hence why it stopped. Any help or experience would be greatly appreciated.

 

I’d say it was debris, or some metal component rubbing on the brake disc.