To provoke some thought...consider
6/2-6/8 Cindy kept Caylee whilst on vacation...Casey ran free & Cindy prolly felt a little taken advantage of by 6/9. IIRC, Cindy had wanted to take off to Cocoa Beach or Ft. Myers (George parents) the preceeding weekend, but, Alex wasn't doing so well...so Cindy went up to spend Friday PM and Saturday w/ her mom & dad. Casey had to be called home in the wee hours of the morning Saturday, 6/7. So both weekends of Cindy's vacation were less than stellar, carefree, vacation-kinda-weekends.
6/9PM (speculation) Casey wanted Cindy to keep Caylee so Casey would be free to goto the Orange County Clerk's office 6/10 to deal w/ the traffic tickets - George could watch Caylee in the morning, right? right!. The flurry of calls 6/9 afternoon to Cindy suggest Casey wanted to drop Caylee @ Gentiva (again). Since Caylee spent the night @ Ricardo's we can speculate Cindy said, something like 'NFW'...prolly pissed after being taken advantage of the prior week.
Sooooo.....Casey got pissed and and said to herself..."Self, its payback time. Let the games begin!" Casey stopped taking Caylee by G&C's 6/10 except, perhaps one or two nights, (e.g Friday night). Casey had to be called home in the wee hours of the morning again Saturday, 6/14.
Of course after 6/15 we know Cindy didn't see Caylee again...but...per speculation above...this was just a big, escalating pissing contest between she & Casey from Cindy's perspective. This continued to build until all hell broke loose on 7/3 when Casey sent Cindy up to Universal on a wild goose chase and Cindy got home pissed off...enlisted Lee's help to create her MySpace epistle and sent him chasing Casey down.
So...from Cindy's little corner of the world...this hide-the-Caylee contest all started when she 'put her foot down' 6/9 after she'd not gotten the vacation she'd wanted. After seeing Cindy operate for the past several months...I'd say she's not one to let go of a grudge easily...methinks Cindy held onto that slighted feeling of 6/9 and Casey just added insult to injury. So..."6/9" was already a prominent date in Cindy's mind when it came time to start talking 'bout when Caylee "went missing" from her life. And that's a little different definition than the rest of us would be familiar with...from the outside looking in.
I agree w/ this line of thinking. I would just add that only seeing Caylee a couple of nights was a huge change for CA and GA. George has stressed several times in his statements that they (KC and Caylee) had been in their home from day one, since Caylee was born. I can easily see how, as you say, in CA's mind, Caylee was, in effect, missing as of the 9th of June. That's when everything changed and KC started staying away or, perhaps in KC's mind, "moved out." Maybe that's why they the rest of the family agreed with that date at first.