Each panel is held on by 5-10mm screws with plastic clips at the edges. These should not have come out IMO. Clips maybe although the front clips mount on the upper lip of the grill apron[clip]. That would take some severe force to move without other front end damage. The panels are typical of under carriage compressed fiber. Not indestructible but should hold up even if submerged. Again IMO.
Now your post caught my attention because I changed my oil last night. I found two screws missing and impact slice through the front panel. I had a valet oil change several months ago and hadn't been underneath my G70 since. So I'm thinking the service department did a shabby job of reinstalling the panels. Even the overlapping flap of the front panel was not attached with the plastic thumb nut that the back shares. So the lowest tech person in the shop did my oil change, punched my panel and lost several screws. I'm pretty sure he changed my oil as I did the previous one with a Wix oil cartridge and the one I removed was OEM. All this valet maintenance kind of scares me. I prefer to do my own work.
So back to your issue. Did someone remove some of the screws or clips to make oil changes easier or some other work? They should be replaced under warranty by the dealer. Or insurance could help. Probably not worth the aggravation. Good luck.
I do love my G70 too.