Help! My custom brushes are gone?

All my photoshop custom brush presets are gone, seemingly without any explanation.

Over the last 6 months I've spent countless hours creating an array of streamlined custom-built brush tools to help my in my endeavors to become a concept artist. Last night I put several hours into a new painting, as I usually do most evenings, but upon re-opening photoshop this morning, all traces of my photoshop brushes are gone. All the presets have disappeared as if a factory re-set has taken place without any notification. No update has taken place, my work-space hasn't been reset. It's simply as though all the brushes I built never existed in the first place.

How has this happened?

Can I get my brushes back?

How to I prevent this from happening again in the future?

This has caused a severe amount of stress and I would really appreciate some help if it's at all possible.

I'm temped to stop paying for Adobe services if these sort of things happen, I can barely afford it as it is. What other unexpected disasters should I be on the look out for in future?

Thanks.