Get the position and size of a floating panel before close

[SciManJD]

So how can I get the last position and size of a floating panel before close? I tried many ways, always without success to get the position. Even if I try to search an ID inside of the component, that stays in the panel to get its bounding rectangle, I cannot fund it. Which is strange, because I see the element ID before close. Then on 'beforeUnmount"-hook it is missing.