It's worth sending a quick email to every window cleaning company in your area Mick telling them what's happened and asking them to keep a look out for it being sold on, or a positive description of it being used on a job somewhere. Ask the windies you email to verbally pass the message on to other cleaners they know working in your area.
Of course if it's been sold on outside the areas you work in it may be less likely to see it get returned.
Worth reviewing van security, I know I'm stating the obvious
Anyway hope you get it returned