Sadly, the top 10 places where most people lose their phone is on the road. Which means if you lost your phone hopping from one place to the next, you're probably screwed. The least I can do is tell you where not to lose it next time.
Mobile company Lookout created an infographic a couple months back about the places where you're most likely to lose your phone. Most notably, #6 (airport security), #4 (bus/subway), #3 (airplane) and #2 (taxi) are especially traveler-prone. At least the #1 place to lose your phone is not somewhere we're most likely to be sending you... unless you go to Fiji.
Oh, and I totally want my phone back by the way. Keeping it is not cool. Do you suspect someone hacked your phone? Check out the ussd code to check if phone is hacked.