That dude needs to pull a trigger, but there is none on your SeaDoo.
I am assuming you have a Merc powered Challenger 2000? The Merc SportJet engine is a monster at eating weeds. But cavitation is easy to see and clear. Quick question, when you took it out after cleaning, you said it would come up to RPM? Did it sound like an over rev? Or normal RPM? You may still have things lodged in there. You should be able to see from the intake side and from the nozzle side.
First thing to check on these is if the reverse bucket cable is still in tact. When he said trigger, he may have meant that stick. Merc SportJets are dual stick in that one is throttle and one is the reverse bucket. If the reverse bucket stays in neutral when you move the stick to forward, it would rev up but not give you thrust. That would be a cable broken or detached. But it also has a lock out mechanism that will not let you throttle up while in neutral, so it would have to be a cable. The stick would move to F or R, and unlock the throttle stick. (not a trigger, but who knows what that yahoo was referring to) If he ordered a cable, it would take a while to get.
The second thing to check is if you have all the tines on your weed grate. SportJets used a spring loaded grate, that was supposed to help clear weeds. Most of us replaced them with a fixed grate. But if a tine broke off, it could have gone through the pump, and that would have dinged up the impeller and pump sleeve. If so, this would cause horrible cavitation and what you are experiencing with no acceleration.
Get back to that dealer and find out what he meant by a trigger, then go out and look at your boat and take some photos of the pump. We can go from there. These are not hard to troubleshoot if your engine is running fine.
The biggest issue, is if you didn't jump overboard to clear the weeds, and limped it back to shore, you could have very well overheated your engine. And that burn down could have caused serious issues. But to that point, you would have not gotten it up to RPM when you went back out. So that is not my concern.
Good luck!