There is a SOLUTION! We had the same thing happen yesterday. This car is a 2024 LR Defender V8. [We also own a 2015 RR Sport which is the love of my life.] We were 6 hours from home and 122 miles from the nearest LR dealership, and over 230 from our chosen dealership. I was waiting for my husband who went into a shop to get us coffee. I started playing with the app. Somehow I locked the car, wasn't paying attention to how. I opened the door, which set off the alarm. Further messing about and the message on the dash said my key was deactivated. We called roadside assistance who said the only thing to do was to tow it, but the distance from the dealerships was outside the range for towing so it would be transport and could take 24 hours. We called our favorite LR dealership and were able to speak to someone in service who agreed that was the only option, since I didn't have both keys, was to tow it. My husband is using my phone the entire time to call roadside assistance, the dealer, our house sitter. It was a disaster.
BUT!!! I was reading this forum and a person way down the page said he was able to get in via his LR app. I had tried that, of course, but it didn't work for me. When I finally got my phone back from my husband I thought how sometimes solutions come in 3's. So I got out of the car, locked and unlocked the car via the remote in the LR app three times, got back into the car and it started. We put it into a better position to tow in case it was something we couldn't start it again. But it was fine after that.
I'm posting this because without the other person's post we would still not be home over 24 hours later. Best of luck.