I’ve been in that situation several times, and I list it as Production Stage Manager with “Take-Over” in parentheses under it. Or PSM with an asterisk, and a corresponding note saying it was a take-over (or whatever word you choose). That might work well if you’re low on space on your resume.
Personally, I’d stay away from “Calling SM” in this situation, since that sort of sounds like there is another SM floating around somewhere who deals with other aspects of the show, when really all problems are your problems at this point. “Temporary” would be weird, too, since you are the only contracted PSM for the show once the original SM is gone, regardless of the length of the engagement.