Unless you find your trashed SIM card, the contacts are pretty much lost.
You can think of it as USB stick or hard disk that had your data, if you throw it away, data is lost.
Partly for that reason, I don't store contacts on SIM card and if I do, I keep copy of it on phone/computer.
In the future, copy contacts over to phone from SIM when changing it and/or keep old SIM around so that you can copy them from it if some go missing.