How do you ask an NCO a question without "checking up"?

Scenario: I needed to get some paperwork stamped at a location across post and a SSG in my company overhead the conversation and he also needed it. He suggested I go with him 1300 next day. Next day rolls around and I had seen him at the company but wasn't thinking of the stamp until 1030 or later when i noticed he was gone. Worked until 1130 and was told to go to lunch and the SSG had not yet returned and I wanted to ensure I would not be keeping him waiting come 1300. I called him to see if he was still going to be headed to where we need to be and so I could follow him across post or ride with (i don"t know where the location is) and he responded "I'll call you back when I'm on my way but it will be a little after 1300." Regardless of his response the paperwork or anything how can a lower enlisted as an NCO a question like this without "checking up" when I should be "checking down"?
Sincerely, PV2 just trying to stay in his lane