Field Values being automatically removed after form submission?

I entered a promo code of GSP0074 into a text field I have on my form. I submitted the form, received email confirmation of my submission with all the order info, then went into the Gravity Forms admin to view my entry from there. Everything looks right aside from the fact that the value I placed in the promo code field was gone. The value for the promo code is listed in the email confirmation but not in the Gravity forms backend. Quite confusing, actually.

Note:I also tried checking the box for showing empty fields to no avail.

I’ve tried 2 additional form submissions using the same data and both appear just fine in the backend as well as via email. Maybe it was just one of those fluke things. I guess it just concerned me a bit because it could be bad if fields have the potential to end up without their values attached to them on the backend. I also looked at the database tables themselves via phpmyadmin and there is nothing there for the field in question.

I can get you the backend info for the site if you feel like poking around or if you would prefer I can just wait on it for now and try and see if the issue occurs again.