Syntax

Oddities of English syntax. The phrase 'why hasn't she been found?' is perfectly idiomatic. But if we expand the apostophe it ceases to be so. We wouldn't, in other words, say: 'why has not she been found?' We would say, rather: 'why has she not been found?' And yet, to expand and then contract the 'not' in it's new location leads to: 'why has shen't been found?', which is also jarringly unidiomatic. I'm not sure why this should be.