You can build a custom LoRa based tracker with 100+km range (line of sight), a van won't disable that. You'll have to use signal triangulation, though, because GPS reception in a van won't be great.
For a custom solution, ExpressLRS [2] is an open source system that can be flashed to FrSky R9mm receivers that you can hack on to add features you want. Or buy Semtech [3] and ESP32 modules and build your own hardware to maximize transmit power (standard hobby receivers only have 25-40mW telemetry)
PS. TTGO LORA32 modules [4] already have ESP32 and Semtech module assembled, only need flashing (again, lower power than a dedicated 30dbm module)
[1] https://www.team-blacksheep.com/products/prod:xf_nano_div_rx
[2] https://github.com/ExpressLRS/ExpressLRS
[1] http://www.phreakmonkey.com/2016/08/towl-telemetry-over-oppo...
They do have an easier job, I think, given that bicycles don't usually weigh between 400lb (sports motorcycles) and 900lb (cruisers).
Their modus operandi is to throw a bicycle into a truck or van, move them in lots of fifty across state lines, and tear them down to components.
Any trackers will be quickly rendered useless once they're in the van, and immediately found and discarded.
I'm definitely planning on getting Airtags for my bikes, but mostly for amusement and occasionally forgetting where I parked, I don't have much faith in them as an anti-theft device.