The man was spotted leaving the cat in a street in Falkirk before running away.
Justin Tosh was last seen in Aberdeen on Thursday, January 28.
Jamie Waugh was last seen by friends at around 4.30am on Sunday, January 31.
Arlo McArthur's mum is urging everyone who can to join the stem cell register to help save a life.
Abbie Macintosh, 16, was last seen on Friday, January 29.