Contraction of past form of 失う？


While looking at example sentences, I came across this on tangorin:

彼{かれ}は視力{しりょく}を失{うし}った。

My understanding is that this is still the verb 失{うしな}う. Searching for the
kana form うしった hasn't led to any results.

If all this is true, why is part of the verb being truncated? Is this a common
shortening?

