This was one reason I did not participate in the MQM promo. I am a President's Circle Member with Hertz, am nobody with Budget and just didn't want to leave the "known factor" with Hertz for the unknown of another rental company where I have no status. Also I did not want to go through the hassle of verifying if each and every Budget or Avis location that I could potentially use actually participated. (Having said that, at the time, I was actually tempted to participate but then I read a post by someone who was burned by a "non-participating" location and my temptation to participate was quickly extinguished.) This happened to you at San Diego, and if it happened there, perhaps there are other locations out there that also do not participate and others could be unsuspectingly burned.
Did you contact Delta about your situation with Budget? Also with regard to a previous poster who asked how you find out prior to a rental if a location participates, I think to be safe you would have to get something in writing at least via email confirming a location's participation to have a leg to stand on when claiming MQMs, miles or whatever. Some employee on the phone saying "sure we participate" might not cut it.. Or perhaps one could email Delta and ask if all Budget locations participate so as to hold Delta accountable. I am sorry that happened to you and it is plain wrong. It goes back to one of my points in my previous post, that is, some people may not mind going through the time and effort to do these kind of verifications and that is their choice which I respect, but I personally do mind and think it is ridiculous that Delta would expect any of us to do so.