I qualified for this challenge with my son Bobcat. I had planned out a set of six caches that met all of the requirements (and then a set of six alternatives in case we DNFed any of those).
But then on the evening before when I was finalising everything I wondered what month I should use for a YOSM. Was it the month that the first YOSM was placed? Or the month that "my" YOSM was placed? I looked on the official YOSM website where it has the published dates for each of the YOSMs. I checked these dates for some of the YOSMs that others had used but they didn't seem to match up. So with no time to get this all clarified we decided to get a different Virtual.
A good challenge. We had a lot of fun doing it.
Here are my qualifying caches (all found 30-May-2015):
Unknown Micro Aug GC4KC8D blank? (Reprise)
Multi-Cache Small Jan GC453VR Church Micro 1416...Woolbeding
Letterbox Regular Sep GC3W2T5 Post Box Letter Box 2, Queens Corner
Traditional Large Feb GC241W7 A272 TravelBug and Geocoin Hotel
Earthcache Not chosen Nov GC389H6 Church Micro 2291...East Dean Chapel
Virtual Cache Virtual Mar GCED7C Sweet Fanny Adams
I decided to pick up the cache this evening. A fox ran across the road as I was approaching. The GPSr wasn't much help but the hint made the cache an easy find.