So up until now I've considered myself to be quite a proficient modder, but after this last mistake I'll have to seriously reconsider my work.
I don't really know what Information you masters may think essential, but I'm telling the story as it is:

Downloaded a House Mod. A very neat little place, and since the Author gave his blessing for people to use it as they wished I thought to give it a little upgrade.
Constructed a New Cell and a few other changes within the original Cell aswell. All this time, since I was going to use this Mod that I had modified, I saved the project as the original File.
(E.g not Save As.. but just a simple save).

When troubleshooting with another mod in NMM I decided to disable all of the active mods, including my House Mod, in order to solve it. Managed to solve it and went back to enable all the Mods again, and this is when I realized my grave mistake.

When opening up the House.esp in CK it was the clean save without any of my changes into it.

So basicly, my question to you competent modders: Is there any chance to recover my lost data? I've put about 70 hours into it and I'm quite ready to put another 70 hours into saving it and possibly redeem my CK techniques.

Also when browsing throught the Data folder I actually discovered that I had extracted the Archives of the Modified House (the .bsa and .bsl).
In the "Backup" folder in Skyrim Main, there's also 9 .BAK files with the exact name of the Mod. (HouseMod.esp.1.BAK)

Any Help would be much appreciated!

EDIT -
Actually solved it by replacing the clean .esp with the .Bak one.

Sort your backup folder by date. The file HouseMod.esp.9.bak may not be the last backup saved. When the CK reaches 9, it cycles back to 0 again, so your latest backup could be HouseMod.esp.4.bak.

When you determine the latest, just delete the .x.bak from the end of the file and copy it to your Data folder. Load it in the CK and take a look.