Lost work due to saving as .html

I was working on a lengthy project, saving all the while. I had about 3 hrs in before I was done for the night. Saved it to documents>sketchup and quit. Today I tried to reload the project, and it just opens to a blank sketchup screen. The file saved as an .html file for some reason, and it appears the project is gone.

Can anybody help with this and explain WHY SKETCHUP SAVED IT AS A HTML???

Would love to not measure the entire house again.

Which version of SketchUp are you using? Your profile says you are using SketchUp 2017 Make but you posted in SketchUp for Web.

If you are using SketchUp Web Free or Shop and you used the browser’s Save feature, of course it would save as .html. If you used SketchUp’s Save, the save action would be to your Trimble Connect storage space, not your Documents folder.
Screenshot - 7_14_2020 , 8_29_26 AM

To save the model to your computer you would have to use Download from the pancake menu, not Save.

You could check your Trimble Connect folder to see if the file was autosaved there. Did you ever save the file with Save as indicated in the first screen shot?