I didn't lose something, but I had something I forgot about and went out and bought anyway. I replaced the 3 belts on my little mtd riding mower, and they did not work right, because the mower is tempermental and only likes the OEM belts. But I had to spend 3 days trying to make the after market belts work, to no avail.
So I ordered a second set of belts being OEM, and replaced all of the bushings and cleaned up the pulleys to the variable speed drive. After spending 2 weeks trying to get the mower running, and finally succeeding, I was in the cellar and came upon a new set of OEM belts for the mtd mower that I had purchased many years ago and had never installed.
I guess it pays to be more organized. Hopefully 20 years from now I will remember I have the belts, and replace them if I am still ticking, that is.