Android app only shows froyo interface

Luckily I had just backed up all of my progress and my app's source code was not ruined. However, if someone could explain exactly what happened so I could never do it again, it would be appreciated.

I translated my strings.xml file and put the copy in a values-es folder. There was an error in the xml file, so suddenly every line of java that referenced the R class was an error. I fixed the xml error and cleaned all projects. Problem solved.

Except now, no matter which version of android the phone was running, the app appeared as if the phone were running froyo or gingerbread. This didn't work to well on my phone running 4.4.4 with no menu key and no action bar. What happened?