As millions of years pass, Vector's body becomes cast in sedimentary rock and he turns into a fossil. The lake where he died has also become a mountain due to tectonic plate movement.
I forgot that my yacht was in the shop, but at least I still have my submarine!
Let me just take step to how you how the sub ... OH NOOO!!!!!
As Vector drowns to his death, his body falls to the bottom of the lake. Since there is not much oxygen at the bottom of the lake, Vector's body decays slower, preserving him as he gets covered by sedimentary rock.
After millions of years, an archeologist conducts a dig and discovers Vector's fossilized body, finally putting an end to the mysterious disappearance of Vector.