It is important to visit unannounced and see how he is living. There will come a time that he can no longer talk on the phone. If he is throwing stuff away, he may actually be hiding some thinking others might take them. Knowledge is important now for planning the future.
Fred.

Move him close to you; make it easier on yourself. This is a "long haul" situation, and you really can't count on others to visit on a truly regular basis.

My first impression is that he is already past the point when he can live independently! You didn't mention driving, doctor visits, any social outlet, other family, etc.
May be time for family intervention, and figure out next steps. Do you have POA, LIVING WILL, MEDICAL SURROGATE DOCUMENTS??? Lots of important stuff to get a handle on!

I think an unannounced visit is absolutely okay, especially in this case. You can see how he's REALLY living, when he can't "clean up" first, and hopefully you'll be able to remove dangerous items. Have you considered what your options are, when he really cannot be left alone any more? Having thought through different scenarios, and having looked at various options ahead of time, can be very helpful later on. It reduces stress, and you'll be glad you did that.

Marcia, Once you have cameras in the house you’ll have a better understanding of how he is doing on a daily basis. Then you can make decisions appropriate to his needs. Right now you don’t have a clear picture of what is happening so you naturally are worried. You’ll still worry but at least feel like you know what is happening and can intervene when necessary.

I hope you can enjoy some time with your dad during this visit.