Cuando volvió en sí, estaba tirado en el parque.

English Translation

When he recovered, he was lying in the park.

tirar means throw away, drop, is it a good translation?

One of the many meanings of tirar(se) is:

tirarse pronominal verb
(Latin America) (tumbarse) to lie down
▸ estoy agotada, me voy a tirar un rato
I’m exhausted, I’m going to lie down for a while