Undoing an event

Yes.... you simply have to look into the folder where the audio from that project is being stored. All the clips and takes are there. The more takes you have done the more clips will be there. You have to look through them and listen to them. I think there is some info in the file names that may guide you to the piano clips. I think you will need to realign them into the project but it's a simple drag and drop back to the project.
 
I know, because I did that very thing..... hit delete after selecting my track, not realizing another track I needed was also selected. I realized it next day. My "UNDO" history was gone when I shut it down the day before.... so I had to dig into the program folder and find the tracks and restore them.
 
 
Edit: there used to be, and still may be a function that lets you "clean up" your song folder. It supposedly goes in and searches for all the non-attached files. The ones that were deleted or not used in the project and removes them permanently. Using this function will reduce the size of your song folders. I've always been hesitant to use this. A better way I heard of some time back was to simply save the song to a new folder and then delete the old one that was bloated with unused takes and blunders.  I have a few song projects that are over 1GB in size with all the takes and attempts to nail something.  I really need to do that sort of clean up. However, once you do that... those files are gone forever. So use that with all due warning. Be sure you're done completely with the old version.