ichidan verb
miss seeing; fail to see
Used when you miss an opportunity to see something, or fail to notice something you should have seen.
映画のラストシーンを見損ねた。
I missed seeing the last scene of the movie.
せっかくの虹を見損ねてしまった。
I missed the rainbow that appeared just for a moment.
見逃す can mean 'overlook' or 'let pass' intentionally, while 見損ねる focuses on missing a chance to see or failing to see something unintentionally.
Compound of 見 (mi, 'see') + 損ねる (sokoneru, 'fail to do'). The verb 損ねる attaches to the continuative form of verbs to express failure or missing a chance.