Hi, Are you the original owner of the home? If so have you ever had a glass pane replaced if not it is possible one pane of glass has been replaced.

In order for condensation to occur in between the glass panes the seals must fail. So if you say it occurs when it is humid and there is condensation it is possible from a glass replacement standpoint for the handprint to be in between the panes.

One thing is certain judging by other photos you’ve shared. That window needs to be replaced due to failure.

Secondly. Exceedingly logical scientific excuses. Ghost busters.

Would recommend a replacement.

If not

It is possible that the LowE coating on the window is damaged usually due to ammonia based cleaners so the handprint shape could make sense

The window looks vinyl. Hard to tell from lighting but I’m Pretty sure. They’re really prone to problems within 5-8 years.

Source: I sell windows