It does not accept miscarriage as an answer while it gives that as one of meanings of the word perdida.
miscarriage = loss of a baby. Duolingo's computer dictionary needs some fine tuning. No human eyes have ever checked it.
Consider yourself lucky. It's a tacky reference to a webcomic referencing someone who had a miscarriage. (Basically, the artist was heavily trolled by the community, who weren't on board with the sudden serious turn of events.) The letters are meant to represent the position of the characters in each of the comic's four panels: standing, sitting, or lying down.
He was trolled because it was so melodramatic (especially because of the associated blog post) and he's not a good artist.
Actually, putting the article in front of an adjective (in Spanish) makes it a noun - el perdido. The lost, meaning the lost one. (I think I'm right about this.)