Seeing that the intermediate beast was patrolling around the storage room, Ian and Vorden had decided to go to a different part of the shelter. As Ian said it was most likely the Portal wasn't there in the first place.
Even though the portal was in a red zone, the portal on the other end still had to be placed in a safe place to make sure either beast from the other planet didn't enter it or destroy it. Of course, a party or a group could bring a portal with them to get back to their own world but these were very expensive.
Somone at Ian's level didn't have one of these devices because once they had been set up, they were unable to be taken back with them. It was a onetime use device.
"Any ideas of where the Portal might be?" Vorden asked.
"My guess is somewhere underground. It's safe from most of the beasts that way. Most likely they have a special building that looks like any other and a secret entrance."
"Wait so are you saying we just have to keep going into buildings?"