I have a small xeriscape front yard with a very fast growing groundcover. It loses it's leaves in the winter. The "vine" is like a smooth tree branch, about 1/2 inch in diameter. It has flowers now of a blue/purple. No garden center can identify it. I can take a photo, but just curious if it rings a bell with anybody.
Sounds like that Vinca, it turns yellow than dies off later when it gets real hot here in Texas. Next year it will sprout up everywhere? That has a periwinkle shaped flower only solid lavender I believe.