See the post by sdsearch above, where they (think they) were finding domestic AA flights that were available for connections to IB long haul but (possibly) not standalone. AA certainly could make their own segments available as part of a connection but not individually (I recall a while ago reports here that this was fairly routinely possible by a request to revenue management if you called in, at least for some AAdvantage members). It would be harder/impossible for AA to make a partner segment available as part of a married sector when it's not available individually.

I don't think sdsearch has demonstrated compellingly that it happened; it would be interesting to see if someone could show that clearly.