You can check on
c:\WINDOWS\Microsoft.NET\Framework\{Version of asp}\Temporary ASP.NET Files\
You can find there a compiled version of your file (if you did not compiled again).
From this version you can recover easy your file by deleting some lines.
Also in this temporary dir, there are the DLL of the compilations, you can find the one you miss and is the page you lose, and open it with NetReflector - there you can get the code you miss with out any problem.
If you have vista, or windows 7, there is also the ShadowCopy, if it is enable you have some of the last versions of your file and you can get them by just see the properties of your file.