key fob security

i had items stolen from my 2002 discovery last night, does anyone know how secure the key fob is, i've done a little research and apparently the encryption is 20 years old which can be easily hacked, i mention this because the thieves didn't break in, the doors were unlocked and i had double checked them when i got home so i am sure they were locked and i mention all of this because yesterday i took my dog for a walk and noticed a pedophile van 50 meters away from me and the people just watched me, i got half a block from the disco when i decided something wasn't right so i went back to the truck and the van left. could they have intercepted the signals from my key fob in order to gain entry later that night?