The only variegated lavender cultivar that popped up on Google was 'Goldberg.' The link below gives some details but doesn't identify a hardiness zone.

I didn't have much success growing lavender in my garden even though I grew several cultivars from seed via winter sowing. A few plants came back the first couple of years but eventually they all disappeared. I'm more of a 'plant it & forget it' type of gardener--if it doesn't thrive on neglect, it doesn't belong in my garden.

Good luck identifying & growing your mystery lavender!

Here is a link that might be useful: Variegated lavender 'Goldberg'

I have a Lavandula x intermedia 'Goldburg' a couple of years ago. It didn't survive the first winter. My experience so far is all Lavandula x intermedia are not hardy to my area. However, this one is so ornamental that I will try it again and again if I can find it again.
I have a Lavandula angustifolia 'Silver Edge' that is hardy to my area but not nearly as showy as 'Goldburg'.