I ran into a bug and lost a large core

I'm going through act 3 of the brutal regime, did a quest to get a large core, but did not activate it, decided to go to the temple of chaos, passed it. When the quests came out, they changed and the portal to the past opened, I thought this was something new and threw out the quest item big Core. When I entered the portal, I was moved to the very initial location, and the activation of the large Core lit up again in the quests. But I don't have it, it didn't fall out when the boss was killed again. What should I do now? is it possible to return the core somehow?

I noticed that if you obtain the cores, then portal out of the area, the cores remain near the portal you used. They drop from your inventory.

Once you enter the portal the cores appear again in front of you.

Now if the portal disappeared, or the zone reseted, I'm not sure what happens.
Best bet, maybe search the map at the place you portalled out from? Or just create a new instance of the map by pressing CTRL.

No, unfortunately updating the map also didn't help, there is no Big Core from the boss.