Correctness and spelling of "misscheduled"

Solution 1:

No, misschedule (or mis-schedule) isn't a word that you'll find in a dictionary.
I agree with @phenry's CMoS citation about not hyphenating words that are prefixed with mis-, as do other sources. Write misschedule if you must.
There doesn't seem to be a concise way of saying that something was scheduled in error; common synonyms for schedule don't seem to lend themselves to something that's any less hideous than misschedule.

Solution 2:

The current commonest usage appears to be misschedule(d).
"Tonight Show will Air at 11pm CST due to misschedule"
"A Misschedule exception is not propagated through two consecutive link events in a flow."

Somtimes, with a single s: "Philly vs Miami... yahoo mischedule?"

Solution 3:

Forget mischedule. You definitely want two S's.

In my experience, people often use the hyphen when they believe they are using the prefix to coin a new word, or a highly unfamiliar one; hence, our willingness to entertain "mis-schedule" when we would never accept "mis-fire", for example. As a rule, though, you should avoid using a hyphen to separate a prefix from its root word unless it is necessary for clarity (you'd want to distinguish "mis-sing" from "missing," for example). So: misschedule it is.

(Chapter and verse citation, if you want one: "Compounds formed with prefixes are normally closed, whether they are nouns, verbs, adjectives, or adverbs." Chicago Manual of Style, 16th ed., sec. 7.85.)

Solution 4:

You'll want to keep the hyphen, as it's an unorthodox or unconventional-ized usage of a prefix on a word that previously didn't have a standard prefixed form.

miss scheduled : mis-scheduled

The hyphen is the clearest way to show that this word doesn't have a proper spelling in your experience.