To keep track of the guesses, I decided to go online to LDS.org and find a list of all the current missions. I cut, pasted and formatted a list of all the missions, combining them by country or state so that I could consolidate them into few pages. I printed the lists out on cardstock and then wrote down people's names as they guessed (on the phone, on Facebook, etc.) and I let people sign their name on the papers directly the night he was opening his call.
I decided to keep track this way instead of the traditional "sticky notes on a map" system because I could easily keep the papers in a scrapbook. I must say that it worked great!
I have already had other friends who are moms of future missionaries ask me for the documents so I decided to share them with the world. I already did the work so the more people who benefit the better! This is accurate as of February 2016. I'm sure it will change and I will try to keep up with editing the missions. Let me know if you notice anything that needs to be updated. Also feel free to download and print and/or edit the documents for free.
Click HERE to get the PDF document on Google Drive
Click HERE to get the PowerPoint doc on Google Drive (you may need to fix the fonts and spacing on that one though)