I often get calls that a student can't find their computer. And, I'll admit, that sometimes I'll put my iPhone down and forget to pick it up. If you have misplaced an Apple device the first thing you should do is go to iCloud.com and use your Apple ID to find it! You can log into the webpage from any device:
There are several tools in iCloud.com, but the one we want is Find iPhone.
Once you select that you will see a map showing all of your devices, not just iPhones.
The example above shows one dot, but if we zoom in and switch to Satellite View (tools are on the bottom right) we see there are actually 2. If you are familiar with BEMS, the 2 dots representing my iPhone and iPad are pretty close to my office Room 54.
If I click on the dot it will tell me which device it is and give me a menu where I can erase the device, lock it, or make it play a sound so you or someone else can find it.
This has saved me a lot of time searching around - I hope it helps you too!