This is an issue we've seen with some builds of 1.8 and has been fixed in 1.9.
Do you have your effects in source control?
If not, you can still recover your effect if:
- you still have the .pkfx.tmp recovery file the editor was prompting you about
- you have a baked version of that effect.
If the last thing you did was baking it, you should be able to get it back by copying the baked .pkfx in place of the source pkfx.
However, baked pkfx are stripped of editor-specific nodes, so any backdrops you had setup will be lost and you will have to re-setup them again.
if you have the .tmp it'll be better, as it's a straight copy of the original file, so it contains all the editor-specific stuff, including backdrops.
Can you remember which compatibility issues you had with Unity? maybe they've been fixed since ?