I had the same sort of problem with a 1994 Mk3.
I had to leave the car parked for quite long periods of time in the staff car park at the airport. Everything was fine till they moved the car park to the end of the runway. People started to report that their car alarms were activated by the power vibrations from departing aircraft or the high energy radar emissions from landing aircraft.
I came back from a trip to find that the key fob wouldn't unlock the door. I used the actual key to open the door, found that the battery was flat then, when I tried to get a jump start, found that the car considered me to be a thief. It took a lot of hassle and visits from the RAC to get it started. After it happened a second time, I decided to try and devise a way round the 'thief' problem. This is what I came up with:
I made up two electrical leads, one black and one red, 3 metres long and with crocodile clips on each end of the leads. The leads were very light gauge, about 3mm copper.
Next time that I had a flat battery, I used the key to open the door then popped the bonnet. I connected the leads to the battery terminals then, because they were so thin, I was able to completely close the bonnet on them.
I made sure that all the doors and boot were closed.
I then connected the leads to a good battery (AA, RAC, friend, passing motorist, etc)
Now there was enough power to operate the door locks so, using the fob, I LOCKED the doors.
Electronically, the car was now back where it started.
I UNLOCKED the doors using the fob and raised the bonnet.
I now disconnected the small leads and used standard jump leads to start the car without any problems.
I used this method about 5 times in the life of the car.
It took me a while to discover that, unlike other cars, the Lexus wasn't really bothered by aircraft landing and taking off...........the real problem was an intermittent boot light switch. Every time I tested it, it was OK........but, every now and then, the light stayed on and drained the battery. Overnight was no problem but, up to a week in a car park, drained the battery completely. The fact that the car park was moved was just a coincidence.