I went on vacation, and drove to my destination. I would say 95% of the time while driving I had no service. I drove on highway 93 in Nevada and interstate 84, across Idaho & Orgeon and interstate 82 in WA, most of the time I had no sevice on my Note 9. I checked the coverage map and it shows that I should've had coverage most all the way. I am really fed up with sprints network coverage... even here in Las Vegas when I go into buildings my phone gets no service... and my girlfriend has AT&T and she had service on her phone most all the way... really thinking about dropping sprint as the network sprint has sucks.....
Couple things could have happened, and this happened to me when traveling as well. I have a Note 9 as well. Sometimes when traveling long distances, and to newer places with towers our phones haven't connected to before can cause interruption.
Performing a network reset during traveling can help the phone remember it needs to connect to the new towers. Especially if a network reset hasn't been done on the device for awhile.
Vegas is a pretty large city, and it is a tourist spot. With that our towers can become very congested, and going inside those large buildings can cause lost signal.
I understand it is frustrating, but some routine maintenance on the device can help improve services usually.