Cap came off front axle trailer

[Riegelman]

On my 2011 T353 the cap on the bottom of the front axle came off which lead to losing all the oil. The cap made of plastic looks like it was held in place with some type of permeatex Hard to believe TYM would “GLUE” a cap in that holds 8.7 quarts of 80-90 gear oil. Anyone else have this problem
Thanks for any help