Missing cat? Missed opportunity.
I wonder how many "poster cats" have ever been found trapped in a neighbour's garden shed? Very few, I suspect. In fact, I'd guess that 99 out of 100 never nick the chicken from their owners' fridges again.
So you might say that the words on posters like the one above don't really matter. But I'd disagree. For me, every word counts. Always. And, in this case, I'd suggest that any of the following suggestions would be more likely than "MISSING CAT" to grab a passer-by's attention, and - just perhaps - persuade him or her to keep his or her eyes open for a feline resembling the mug-shot:
OUR CAT IS LOST!
HAVE YOU SEEN OUR CAT?
PLEASE HELP US FIND JOSH.
COME HOME JOSH, ALL IS FORGIVEN!
Of course, it probably wouldn't make any difference to the ending of the story. The chances of poor old Josh returning home safely would only be very marginally improved (say 2% rather than 1%). But writing persuasively is about using the right words to increase the likelihood of achieving the result you want - even when, as in this case, it's the longest of long shots.