A Small Chance To Get A Full Key

There should be a small chance for one of your fragments to be a full key. The system would count it as receiving a key fragment and would adjust the chance of finding another one accordingly. This chance would be very small but I think it would be kind of awesome to just suddenly get a full key and i think it would reduce a lot of the frustrations with the rarity of key fragments compared to how many chests you get.

Thoughts?