Contacts app not showing all contacts!
From the surface clues, I thought the index was corrupt. Not the issue at all. Being a newbie to the Android, I was unaware of all the myriad features of the beast:-)

A lot more digging found the "problem". Namely, I use lots of category designations in my Outlook contacts. MyPhoneExplorer does a 100% correct job of transporting all these ... BUT, turns out the Android contacts app in its FILTER option treats these in a bizarre way. Namely, if you try ...

Contacts->->Filter->Display contacts->Local

... you see that ALL the existing categories are checked ... BUT, the very bottom one ("All other contacts") is NOT CHECKED. The result is that all contacts WITH categories get displayed, and any without a designated CATEGORY are NOT displayed.

Simple solution (discovered after a week of hell:-)) ... just check the "All other contacts" box, and PRESTO! Now I see everything.

Post-script: whoever designed this "Display contacts" feature has it backwards! The default should be to show ALL contacts, with option to the user to narrow the selection by UNCHECKING various boxes.