Wow! That stinks… sorry to hear that.
Question: was there a major temperature change over night? I wonder if it had a defect, perhaps a small crack prior to cleaning. I’ve never seen a double pane window do that… not from WFP anyhow. I would have the manufacture look at it…
Personally, I would talk to the home owner and see if it’s under warranty. Then offer to pay any damages if the manufacturer determines it was indeed your fault. If they determine a different reason your clear.
I’d suggest researching the manufacturer as well and see if there are any similar cases or even a class action.
Is it an Andersen or Eagle window from the 90’s-early 2000’s? They had a lot of issues with outgassing, and will implode on themselves. Sometimes the small amount of stress from cleaning is the last straw and they’ll fail shortly afterwards. Not your fault, you might’ve just accelerated the inevitable by a month or three 
Wow! you learn something new everyday! I had no clue. I’m going to backlog this just in case something like that happens to us.
Where are you on this? What was the finale?
The end was I paid 300 for a new window for the customer . I dont think there was a chance it was my fault but had to take care of the customer.
Lay a straight dowel across the pane of glass on a nearby window to see if the glass is bowed. May be a manufacturer issue?
An argument in favor of doing things the traditional way nose to the glass from a ladder. No guess work. Ya never really know what happened to banged up wood work and scratches on the glass when it’s 30 feet away.
It’s always your fault because you kinda weren’t really there to say the customer is wrong. At thirty feet your opinion is only a hypothetical idea.
I do most first-time cleans nose to glass. But even if I had to replace a $300 window every year, I still wouldn’t give up my wfp for doing maintenance cleans 
As it is, I’ve had one failure like this in the last 13 years, and the customer had no interest whatsoever in having me pick up the tab. They understood it was due to a defect and I did nothing wrong; just bad timing.
The last to touch it is the first to blame no matter what the cause.
I’ve heard that’s often the case. I must be particularly fortunate with customers. So far I’ve paid for only the stuff I really broke myself. And I know that they’re not just “being nice” about it, because they always have me back for repeat services.
Actually, there was that one time I paid for a car hood to be repaired and repainted, because I apparently knocked an icy chunk of snow onto it while shoveling a 3rd story deck. I still think it was from icicles that fell off the roof, though.
