That one caught me the other day (shortly after an Android OS update). I only saw it once, with the button down at the bottom of the screen. I can't seem to get it to do that again when I try calling my phone from another phone.
Also, your report is the only instance I've seen to confirm that this happens -- for whatever reason no one believes me when I post something about this to any Android group. Just like I seem to be alone in trying to figure out how to get the Contacts (when launched from the dialer) to show only specific groups (such as contacts with phone numbers). I can do this from the Contacts app, but not the Contacts tab inside the call dialer app.
Also, your report is the only instance I've seen to confirm that this happens -- for whatever reason no one believes me when I post something about this to any Android group. Just like I seem to be alone in trying to figure out how to get the Contacts (when launched from the dialer) to show only specific groups (such as contacts with phone numbers). I can do this from the Contacts app, but not the Contacts tab inside the call dialer app.