A flower grew in my yard which I did not plant. Yesterday it was incredibly beautiful, but today it has already started to wilt.
It has a very long 3-foot stem with the flower at the top of it:
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If the leaves are sword shaped, that is a Bearded Iris, botanical name Iris germanica, not sure which variety, colours are too faded to tell. Similar one shown further down in this link, but there are many colours and colour combinations
Better in sun, the rhizomes at the base need to bake to some extent during summer for increased flower production. Conversely, flowers usually last a few days, so long as they're not in hot sun, which frazzles them quickly. Thus proving the old saying 'you just can't win'... However, I don't know where you are, but these usually flower earlier in the UK, certainly before end of May, when the sun is not usually that hot.