Future fixes happen more quickly with the almanac, rough current location and current time already on board, the receiver knows exactly which "birds" should be visible. It often has 12 concurrent receivers on board. Each one is handed a PN sequence matching a desired satellite. The lockup can be as quick as 15 seconds on a "warm start".
Cell phone get a time stamp off the tower. You get that running start of general location and time. Some can even pass the almanac from the tower. CDMA phones have AGPS. They can leverage the known GPS coordinates of a tower to get a jump start on the positioning calculations or even ask for them to be done as "a service" using precise time offsets to the phone.
Back to the original point. GPS can be done purely passively. No transmissions required. If you have a cell phone, you can leverage the connectivity to save the lag time of the typical GPS cold start. GSM phones can perform a high resolution "ping" using 3 towers to get a pretty decent fix on your with the time offsets. Much of this technology exists per the E911 mandate. It is required to locate any cell phone within 100 meters to support law enforcement 911 services.
Stealing the cell phone was the criminal's mistake.
Bingo! I called Verizon and asked if there was any unusual traffic on her number and they confirmed it. I explained that the cell phone had gone missing and I suspected it had been stolen. They gave me a list of the recently called numbers. I started working my way down the list.
The fist several were time and temp calls. I got a couple of businesses and at least one confirmed they'd gotten a call about a carpet cleaning appointment. The next was a private residence, After I explained why I was calling, the woman said, “Not this again.”
It turns out her brother-in-law worked for a carpet cleaning company and she gave me the BIL’s name. I called the company and explained the situation to the boss. He was aghast and I told him I'd keep him informed. The next phone number got the employee's home answering machine, so I left a callback number. Then I called the sheriff's office and filed a complaint.
Several hours later I got a call from the BIL. He confirmed that he had the phone, but he maintained that his partner had taken it. I explained that the stupidest thing he'd done was to use the phone because every call he'd made was logged with the time and length of call. Caught, the BIL tried to weasel out. I told him that he'd be visited by the sheriff's office because I'd filed a complaint. I told him that the best thing to do was to turn-in the phone to his boss and he agreed. It was done, I got the phone back, and the BIL was fired.
As part of his plea bargain to avoid jail time, the perp repaid me for the calls made plus my time and effort tracking him down. It took two years but the settlement was the ultimate satisfaction.