Time Machine Back-up problem

Yesterday I decided to upgrade to El Capitan. I did a Time Machine back-up of my Yosemite HD. I then booted from a El Capitan USB drive wiped the machine and installed from scratch. Everything worked fine. I plugged in my Back-up drive and backed up my new El Capitan Build.

Today I opened up that drive and it didn't have my Yosemite backup. Only the one I did with the new El Capitan build.

Needless to say I lost lots of stuff.

I just assumed it would keep all my older back ups.... Bad move on my part.

Anyone have any ideas on how I might recover the missing stuff. I have ProSoft Data Rescue and did a Quick Scan but it didn't find the Yosemite build. I'm doing a Deep Scan now but not very confident it will find the stuff I need.

Any ideas or suggestions would be appreciated.

thanks! Mike