I was cleaning out my freezer and found a tray of ice from the summer...

... and i could swear that the ice cubes "shrank" over the months.

Is this possible and why?

Or do I just not remember how small they were when they were freshly frozen?

That is called sublimation.

Just as some of the water molecules in liquid water escape into the atmosphere, which we call evaporation, some of the water molecules in solid water (ice) escape into the atmosphere.

It is much harder for water molecules to escape when frozen than when liquid, so sublimation goes very slowly, but as you've discovered, it does happen.

The ice does not melt and then evaporate. The water molecules go directly from solid to gas.

Well maybe they melted a lil bit everytime the light turned on lol I think you just forgot