If you have Boost Loopt installed on the phones that you lost then the phones must be turned on to locate them on the map (GPS) otherwise if it is powered off then it won't do any good. However you must have another boost mobile phone to setup to communicate with the lost phone.

Boost Loopt is known as a social networking application so that you can communicate with your friends and know their location. I don't think this application is used to search for lost cell phones.

My best advice is to contact Boost Mobile Customer Care and ask what you should do since you lost your cell phone.