Hello, I am really sorry to hear that Buddy is still uncomfortable even with Robaxin (methocarbamol).
It isn't at all uncommon for the adrenaline released while they are at the veterinary clinic to over-ride significant pain and make it very difficult to find the source of pain when we are examining our patients.
I am not surprised he is still uncomfortable because while Robaxin eases muscle spasms it doesn't help the primary source of pain, which is pressure on the spinal cord or the nerve roots.
Veterinary drugs we can add include steroids or a nonsteroidal like Metacam, Deramaxx, Previcox or Rimadyl as these will reduce the inflammation and pressure on the nerve(s) which is the primary source of his discomfort. If those aren't enough we can add another drug in the opiod family called Tramadol and/or another drug called Gabapentin.
I understand that you don't wish to overmedicate him but by using an anti-inflammatory (steroids or nonsteroidal anti-inflammatory), a muscle relaxant like Robaxin, and a medication purely for pain such as Tramadol we can use lower doses of each and get him much more comfortable. If he cannot rest and relax he won't heal as well or as quickly.
Best of luck with Buddy, please let me know if you have any further questions.