Upvote:2
The diagonal lines mean your exit from Schengen was cancelled, which is indeed exactly what happened. The stamp itself has no impact on future travel to Schengen or other countries.
However, you have now technically been refused entry to Croatia. Since your passport was not stamped with a refusal, this was likely processed as the Croatian equivalent of "withdrawing application to enter", but you may wish to err on the side of caution and state "yes" if you're asked in the future whether you have ever been refused entry.