You must have been within 3 miles of the coast. I have taken the trip up the Jersey coast numerous times and had no signal for sustained periods 5 miles offshore. Cell phone are not a reliable means here, For what its worth I would have a PLB as well as VHF and cell phone. The PLB is absolutely waterproof itself and doesnt depend on waterproof packaging.
Also Lost signal from Montauk to Block as well as Mystic to Block last year
I currently use ATT. Maximum range for GSM is about 20 miles, or line of site. CDMA has an even longer range, I think, but I'm no expert on any of this.
It's possible I lost signal off the Jersey coast, but wasn't paying attention to my phone.
I sail to Block Island from Mystic several
times a summer and have not lost signal in years. Hell, a buddy and I are known for sailing over, having lunch and a beer and sailing back. My iphone plugged into my stereo, listening to Pandora radio all the way.
I used to get charged roaming (back when they charged for it) from my dock in Mystic as my phone would pick up towers on Long Island. I would have to call Verizon every month to dispute the charges. Some dipstick on the other end would argue with me every time say that I MUST have been in NY!
Montauk to Block I can't vouch for as I don't normally go that way but I can see how it could happen.
Anyway, many of us stay within cell phone range for a high percentage of our sailing time. Many of us also have a device that is a chart plotter, GPS, compass and phone that we have in our pocket much of the time. It's worth several hundred dollars and we spend as much of our time as possible just a few feet from water over 6 feet deep. My point is that you might as well invest in a water proof case.
And again, I'm not saying a cell phone is a replacement for a VHF. Just a happy addition to the family.