Just relooked at mine and it has no ribbed cover. There are 2 tubes that connect to the emission system, 1 additional short tube is a vent and 1 electrical sensor connector. This would be a Ford item versus Forest River item if my guess is correct. This may help in your search.
The ribbed section on yours might just be a cover over an internal tube. As long as the tube is complete then no issue. If not, and it is what I believe, then you will eventually get a "Check Engine" light on the dash for emission control system problem.
Mark & Connie
2020 GT5 31R5
2006 GMC Canyon (Toad)