1
general::
Phrase(s): catch sight of someone or something [and] catch a glimpse of someone or something
to see someone or something briefly; to get a quick look at someone or something. • I caught sight of the plane just before it flew out of sight. • Ann caught a glimpse of the robber as he ran out of the bank.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
See suddenly or unexpectedly, as in When I first caught sight of the Alps, I was overwhelmed. [First half of 1800s]
American Heritage Idioms