One random layer in my imported Illustrator file has stopped working, Because Reasons

[jonk74258691]

Hello everyone! I am currently doing an Aftereffects project with several imported Illustrator files - they've all gone in  fine and given me no problems.... right up until ONE random vector layer in one file decided to stop working, leaving me with this:

What makes it worse is, I have no idea when precisely this happened, or what caused it to happen - I noticed it right after I imported another, fairly minor Illustrator file into the main comp; but I don't see how that import could have done anything, as it doesn't connect with the layer-glitched one in any way. 'Reload footage' breezes by the quote-unquote missing layer as if it doesn't exist, so I'm rather stuck as to how to recitify my brand-new first-world problem....  

[Rick Gerard]

Open the original AI file and make sure that the layer is still there and the layer name has not changed.