Those would go on the balance sheet and on the shareholders' basis schedules.

Do you think it's appropriate for capital contributions to be put under capital stock? Weird that the IRS doesn't provide instructions for this as its common for shareholders to contribute money into their S-Corps, especially when the S-Corps are incorporated.

Were they issued more stock for the money or did they just pay in additional capital?

"Weird that the IRS doesn't provide instructions for this"

There are accounting standards for this, though. Are you reading the questions and going to be providing answers? You were asked:

"APIC?

SH Loan?"

"Do you think it's appropriate for capital contributions to be put under capital stock?"

Do you? You were asked:

"Were they issued more stock for the money or did they just pay in additional capital?"

More details always matter.

No additional stocks were issued. Just that the shareholders contributed more money to fund the S-Corp.

That's called additional paid in capital.

APIC may/or may not be allowed per state law.

And the IRS 'has' addressed this - see the basis computations/analysis and the relatively new Form 7203 reporting at the F.1040 level.