Portal on heist dissapearing

There's no point to put a screen shoot since I didnt except it to even happen. Around the time 5:00-5:27 p.m (GMT+2). I was doing a grand heist on Prohibited Library with 4 wings revealed. I did finish the first one in which i got a replica and then i got out to empty my inventory and then i gone in again. I was full so before I choose my item, I gone out to empty my inventory again. And when I did finish it and I was about to go in again the portal was gone. It did close before I finish my other 3 wings.