My wife and I saw a rectangular shaped object that was lit up in the night sky.

As I was driving eastbound on Bluemound Road my wife and I noticed a rectangular shaped bright object in the twilight sky. It was stationary for several minutes and then abruptly disappeared. It was at a very high elevation. This object was not a helicopter. We frequently see flight for life helicopters landing and taking off from Froedtert Hospital which is in that area. However, this object was different and at a higher elevation than the helicopters we typically see. What surprised us the most was the abrupt disappearance. My wife who is 70 retired from teaching in 2007 and I retired as an Electrical Engineer in 2017. I am 66 years old.