Stendel has emerged as Hearts owner Ann Budge's first choice to succeed Craig Levein but his situation is complicated by the fact he remains contracted to Barnsley for the rest of the season.
Hearts had been very close to making an appointment and could still do so before Wednesday's visit of Livingston, for which MacPhee will be in control of the team no matter what.
But Barnsley chief executive Paul Conway intervened on Tuesday morning by publicly demanding compensation from Hearts should they appoint Stendel.
The German led the Yorkshire side to the Sky Bet League One title last season but the club announced they had "separated from Daniel Stendel with immediate effect" on October 8.
Quoted in the Scottish Daily Mail, Conway stated Barnsley had written to Hearts declaring they would expect compensation if any club "tampers with their rights" regarding Stendel.
"Hearts have our letter and we have notified them and, if they want to hire Daniel, that's fine, that's their choice," he said. "But they either pay us now or we will file a claim against them. And if any club wants to fight it, we will win."
MacPhee, speaking at a pre-match media conference, admitted he did not know if Wednesday's game would be his final match in charge.
"I honestly don't know," he said. "Obviously there are talks going on with other people and I will speak to Mrs Budge again today (Tuesday) at some point.
"If there is anything to be communicated, I will always do that with the players. She has very good lines of communication with the senior players as well.
"I still think it's the right thing that the right decision is made and it's got to be a decision the board believe in.
"Just because whoever the manager they want to put in post isn't available or it's maybe more complicated, they are better trying to get whoever they want. Especially given the run of games."
MacPhee has lost three of his four matches in charge, conceding 13 goals in the process, but was at pains to stress that losing twice to Rangers in Glasgow was not out of keeping with historical trends.
And he claimed a new manager was better taking charge with a less difficult run of fixtures, citing an example from across Edinburgh.
Hibernian sacked manager Paul Heckingbottom a week after Levein lost his job but new boss Jack Ross has been in charge of three matches, winning against Motherwell and St Mirren before drawing with Kilmarnock.
MacPhee said: "Hibs is a good example, he has come into post where there are very, very winnable games, and that gives the appointment momentum.
"There are so many games between now and January, it's important these things happen at the right moment. If I have to take the team for some more awkward fixtures, I have no problem with that.
"I know the club are working on what they believe to be the next best step and sometimes these things take time."
MacPhee – who has been assistant under Ian Cathro and Levein and would be interested in taking over as the club's new sporting director – claimed he had not held talks with Budge over his own future.
"She has just asked me to proceed with taking the first team," MacPhee said. "I am just focused on that.
"The other things going on in the background, I don't need to know what they are. I just need to focus on the game.
"It's a massive three points for us. We need to get the team on the front foot, get the supporters behind us and get the type of performance that got us three points against St Mirren."