Job interview coming up, but interviewer hasn't confirmed the date - how to remind him without being pushy?

I had a phone interview yesterday that went really well, and the phone interviewer informed me that I would be meeting the head of the department very soon for an in-person interview.

Later in the day, I was provided with the department head's contact info and instructed to reach out to him via text to set up the in-person interview.

I texted back and forth with the department head yesterday evening, and he informed me that the interview would take place next week at a nearby restaurant for a lunch meeting. The problem is that he never specified which date (Monday, Tuesday, etc.) we would meet, and he didn't reply when I asked him for that information. Basically, all communication from him ended after telling me to be at the restaurant at 12 noon next week, with no date provided.

This morning, I texted him again (in a very polite and friendly manner, of course) to request this information. Still no response.

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My question:

How would you recommend that I reach out to him without coming across as pushy or desperate? Would it be weird to contact the phone interviewer and request his help? Or should I wait a bit longer?

FYI it's been almost 24 hours since the last response from the department head regarding next week's interview.

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