Touch wood I've never left anything at a job or had any gear lost/stolen. But given that 99% of people are pretty honest, I put my phone number on every bit of gear from bodies to light stands. If you picked up a Pocket Wizard with a phone number on it, what would you do? Some mongrels would pocket the item but by far the greatest majority would make the call.
Put your number on everything. I use a label maker. At least you're in with a good chance!
It is nice to be so positive, and it may work if you leave/forget your equipment somewere... but what about someone whose steal it on purpose? I think he is not going to call you...
And i Think thaf very few people forget their 5DIII + 200 f2 somewhere. But if they put telephone number on it, they may be luky.