Dust caps fall off

[BMS]

So a dust cap fell off of one of my 6 12s i noticed because that sub was running cooler (they are inverted) I am still braking them in but the weird thing is i didn't seem to notice any performance difference the pole vent is probably 2.5 inch in diameter and maybe 5 inches long from bottom to top plate and now that hole is in my box. I have a db meter the only problem is ive been breaking them in and i dont know when it fell off so i dont know how it is affecting my system but i did NOT notice it get quieter at any point. This should be a major performance issue correct? im still hitting 151.9 at 27 hz and im not really pushing them so im just confused as to why i dont notice a huge performance difference? What should i use to reglue it i think the manufacturer used a cp moyen apoxy (the back stuff) on everything including to glue the dust cap to the cone which i think the cap is paper carbon fiber reinforced and the cone is pulp paper.