I know I'm a year late and a dollar short in answering your question My Dh too lost the "strum," ringtone and it ISN'T listed in the classic ringtones section either. After there is an Apple software update, sometimes there are glitches involved. Here is a solution in case you haven't solved the problem. What you have to do is to do a search on google for the "strum," download. Then send it via email to yourself. Click on the link and then download it on to your desktop. Connect your iPhone on to your computer and go to iTunes ringtone section. Then drag the ringtone on to your ringtones section. The "strum," ringtone should show up as a new ringtone at the very top of the ringtone list. Click on it and you'll have your strum back. Good luck! -Ella
See last posted suggestion - it works! Strum is back!
What you have to do is click on this link: http://www.zedge.net/ringtone/1653667/
Then send it via email to yourself. Open the email on your phone, download the attached mp3; click the little /\ arrow on the right hand side - it will probably be pre-checked to your iphone.
Look under classic ringtones and it's there! Thank you della_riata