it does not dissapear. But Polish spelling rules say that
ś+ vovel is written as si+ vovel,
and ś+ i is written si.
those are also rules for reading (reversed), and apply to all "dash" letters- ć, ś, ń ź dź
so it's basically a different way to spell the same sound? also dź is a letter?
and dź is two letters one sound, like cz, sz, ch, rz, dz, dż. (or English "th")
I wrote "We haven't any geese". That shouldn't have been marked wrong.