It appears my stimulus check has been deposited into that intermediary bank used for my tax refund. Is there a way to contact the bank to learn the status of my $1200?

The company that handles your Federal tax refund when you choose to pay fees out of the refund is SBTPG.  Normally they close that temporary bank account after your refund has been sent on to you.  If that's the case, then when the stimulus funds were sent to a closed account, SBTPG would likely send it back to the IRS, who would issue you a check in the mail in the next couple weeks.

I have no way of knowing if that's what happened to "your" stimulus money or not.  You can phone SBTPG and ask them if that is their procedure.  They may be able to tell you if they received it and sent it back to the IRS.

SBTPG has a phone contact page at the following link. It also shows their business hours.

https://help.sbtpg.com/hc/en-us/articles/230084587-Contact-Information