Well I wouldn’t let one bad guy turn you against anyone. You are and have become educated. I would suggest to you though that your minds eye isn’t necessarily the best judge. Shop with your wallet…look around, there has to be someone of repute that won’t “mess” you up. Sometimes changes have to be subtle and over time. The point I was also making is that you are not going to throw at max velo every time you throw, don’t get so down in the dumps, was it a good bullpen besides speed? Did you hit your spots, change speeds, have movement? Always honestly assess your training in terms of the big picture. If you were completely bad, well, shrug it off, re-dedicate to your mechanics and get back at it.
DM has an excellent point. You more than likely need to analyze your training regimine to maximize focus on areas where you need to improve and leave behind stuff that isn’t as helpful.