My question involves police conduct in the State of: Texas

So question about this. I recently got a speeding ticket (link to other post) and during the traffic stop, the cop opened my car door to scan the sticker/barcode on the inside of the door frame.

This was shocking but it happened so fast. The cop just did the scan and then closed the door again.

Curious to your thoughts on this? This seems like quite the invasion and illegal search and could easily be used for developing probable cause....