catch sight of (someone or something)
To see someone or something very briefly or suddenly. Wendy only caught sight of the burglar for a second, so she couldn't describe his appearance to the police. I didn't know what the bunny was running from, until I caught sight of the dog that was chasing it.
catch sight of someone or something
and catch a glimpse of someone or somethingto 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.
catch sight of
See suddenly or unexpectedly, as in When I first caught sight of the Alps, I was overwhelmed. [First half of 1800s]