My boss was very disappointed when he went to Blackhat and Solarwinds was not their, sends a really bad message.
Did some googling and it looks like SolarWinds doesn't usually go to blackhat, at least they have never been mentioned or promoted having a booth there anywhere that I can see. So I guess the question is why would you have expected them to be there?
I would expect any vendor selling security related products at Blackhat, but today it seems like lowering expectations is the modus operandi ;-)
You have touched on the truth of the matter, despite having a few products they acquired over the years that are kind of in the security space, and despite what the marketing team wants to pretend, SolarWinds has never been a serious security solution vendor. So I guess not showing up to Blackhat (or any other particularly security-centric events) sends exactly the message that your boss thinks it does.