I installed Yosemite PB 3, and when things went south for me (twice), my mistake, not Yosemites, I just hit the Command key, and R, and away I went with the install again with Recovery though I could not see it in Disk Utility. It just worked
From now on I use Time Machine to make a complete back up to a 32 GB thumb dive, and I tried this for Yosemite to see if it works. I hit the Command and Option key to get things going, a box appeared that allowed me to click on Time Machine, and this took a few minutes with a SSD drive. All was returned to normal without going the Recovery method. I have two USB thumb drives, for Time Machine just in case one goes bad.
Hope this helps