Yep. It's not a situation where they're an indeterminate way through building a custom app using a custom framework and you really do lose everything if you start again, it's a case where an agency has designed and handed over a logo and some very conventionally-designed mockups which any competent freelancer with knowledge of Vue should be able to implement on your platform, and revise as requested. And they're citing lack of availability, so it's not even rude to walk away with the deliverables you paid for.