It is not part of a train. I have spent the last 17 years as a Freight Car Inspector, and am also familiar with locomotive parts. Most, if not all parts found on railway cars and locomotices are made of forged steel, formed steel or cast steel. Sheet metal parts are rolled and formed, punched and welded in place. Assembled parts under modular construction techniques are usually anodized or painted. Most all are ususally filthy with road grime, unless new. I have looked at these pictures and have thought about all the parts I have become familair with over the years, and I cannot make this chunk fit into any scenario.

The tag is a sticker by computer generation, similar to inventory control stickers. Most new parts come this way, but they don't ever desginate railroad ownership, only part numebers or assmbly process controls. UP 9999 doesn't mean that it's from a Union Pacific train, anyway. UP 9999 could mean anything, and it might only be one of several stickers from the part.

In my opinion, the guy backed his SUV into something and this part broke off in his hatchback. Given that it appears to be made of a cast metal or composite ceramice, it would have brittle qualities, making it easy to break apart. If it launched from somewhere into his SUV, there should be 'crumbs' under his bumper form impact, and likely other pieces in the path from whereever it came from. Anyway, I bet he accidentally backed into something pretty hard, like a piece of machinery sitting at a dock or job site, broke the hell out of whatever it was and decide to scram.