Objects Randomly Disappear This isn't the first time that this has happened to me. This also happened to a different project I had 2 months ago in version 2.8.
Objects would just disappear the next time I open the project. Yes I checked if they were in a hidden collection, I kept toggling / , and I tried Alt + H . The first picture was a test render I made, and the second is what it is now from the same view.


There is no way that I accidentally deleted them, since staircase is made of 3 separate objects and I would have to select all of them at once then delete them. Besides that, other objects in different locations also disappeared at the same time.
The one thing I noticed is that the objects disappear after open and start working on a different project. There is no particular order that they disappear either. Below is a couch that I modeled. The main cushion was the first one that I made, followed by the 4 large pillows, then five smaller ones (The three in the middle and two on each side that were leaning on the arm rests). Even though I made the cushion first and the small pillows last, they both disappeared, along with a table I modeled many weeks before the couch itself.

I need help to somehow find out how to recover the objects and/or prevent this from happening again.
edit: screenshots of my outliner
Try to press the 1 button on your keyboard (not on numpad) in object mode. You are maybe viewing different layer. This happened to me a few times.