what should I say?

Yesterday my colleague told me "Charlie (her dog) went missing..."
and I didn't know what to say to her.. so I just gave her some "hopeful" words..
"Don't worry, perhaps he's just having some "fun" time."
Another colleague told her "Try to search inside the drain. Sometimes they fall inside but don't know how to get out."

At night I messaged her, asking whether she found Charlie.
She said they still couldn't find him.
The only words I could say is "Pray that he's safe and he'll return to you soon.*hugs* Take a good rest. I know it's tough but try to catch some sleep."

It got me thinking of how I lost my dogs.
Happy (my first dog) went missing once. I was maybe 8-10 years old (not sure). I was very sad when we couldn't find her. However, the person that "took" her returned her home. Asking for some money. I could still remember my dad coming into my room telling me "Look who's back?!" (it felt like a dream when he asked me) I sleepily answered "Happy...". I didn't wake up immediately, I guess I was too tired from worrying and crying.
The next morning I found her running around inside my house and my dad told me the story above! :)

Well, animals come and go, just like humans.

Throughout my 24 years, I lost 2 dogs, Happy & Shaggy.
I still have 3 with me, Pingu, Tomo & Kai Xin.
It's great to have these furry creatures in my life but it's sad to know they'll leave you some day. It's sad but true...

but what words should I use to tell her that "everything will be ok.." ?