I understand EXACTLY how you feel. Took care of a Little girl from age 6mo. to 4yrs old. Just had the Mom call with 2 wks notice. Apprntly she has had her daughter on a preschool wt list (with after care) for a while, plus she just had second baby (I didnt know she was pregnant until past 4 mo.) It def "hurt my feelings" a little, because I felt like I was almost lied to because she never let me know what her plans were. Thats pretty much what seems has happened to you, these people went with you for 9 mo. but knew all along they were waiting on a list for centre care. We all have to remember this is a competetive field...IF they had been honest with you about being on wait list for centre (because they feel centre care is best/their choice) you may not have taken them, they needed care while waiting and you were the best care they could find. Take that as a compliment. It does stink that they werent honest with you though, maybe you could have taken them contingent and given them notice that if a perm dck came along they would be bumped? Bottom line: we all do what we need to do, parents and providers, they did what they had to do to get quality care while waiting for what they really wanted all along. too bad things couldnt have been dif.
not sure if it helps but: I always tell parents in first meeting "i am a very honest and open person, I give ALOT of respect and expect ALOT in return" I expect open communication regarding ALL things. not sure if that would change your situation but may lead them to think about telling you in the future. (although it didnt change this sit. w/ me either)
Maybe you could add a clause to your contracts: if a child leaves for any other reason than school age or disatisfaction with care, 4 weeks notice must be given for time to replace the child?