Possible gameplay bug in Entrance Hall [SPOILER]

[Mephisto]

When you have created the acid mixture in the laboratory, then applied it successfully to the tissue blocking the entrance to the refinery, you may come to think "Wait, why not get another fill of this for future use". Smart thinking!

So, you travel back to the laboratory only to learn you can't get a second fill! Doesn't work anymore.
When you come back to the refinery entrance, the tissue is back, and no more acid mixture!
At least that's what happened to me.