I Got Blamed For A Mistake That Wasn't Mine & Lost My Client Because Of It, What Should I Do?

I've been working with a client who runs an automotive business on helping them with their SEO so they can rank higher in their local area and while I've been able to help them over 3x their call rate over the last three months I was immediately fired for a mistake I didn't even have anything to do with. It's super frustrating and even typing this I'm still angry but I'm not really sure what to do about it so I figured I'd reach out to the community who might have some idea, let me explain the situation...

So as I mentioned I do SEO for this automotive business and for my SEO services that include both internal and external website changes to enhance the website's search appearance. Now normally I tend to become my client's web development and SEO team because there are a lot of crossovers between the two, but this client already had a set web developer and while it's not always common I was okay with it because it's really whatever makes the client comfortable. Well anyway, things were going well until one day the website just suddenly crashed. I only know it crashed because I woke up to a series of panicked texts by the owner saying he couldn't get on the website and asking what I did. Upon further investigation, I went onto the backend of the site and found out that a number of plugins that were outdated had been updated and were no longer compatible with their original builder causing the site to crash. I informed the owner and he told the web designer in order to fix it.

A couple of days passed and nothing had changed until eventually, I received a text message from the owner saying that "Because of recent events he would be stopping SEO work as whatever I did ended up crashing the site" not the exact quote but super close. Apparently, his web designer had told him it was my fault and because of my more recent relationship, he sided with the web developer. Is there anything I can do or say?