That is actually a possibility. I am assuming they are lost as I have not seen any of them poking out of the water on Google Earth - though they could be submerged completely.
Of course, a truss with no floor is sometimes impossible to see on Google Earth.
Are we sure these bridges were actually removed? Sometimes they just left the bridges in place and they remain underwater in the reservoir.
This bridge would have been inundated by Hillsdale Reservoir. Thus we can consider the bridge to be lost.
KSHS page with photograph: