That would have been the correct enforcement IF the foul happened during the running play part of the down and IF the foul was at the 37. (Did you see a flag there or just going off the announcer claiming there was one at the 38?) It is definitely possible #76 moved downfield and committed a foul at the 37. The act the announcers were claiming was the flagged foul was iffy anyway. He may have done something worse further downfield.
The official stats say:
Cin 1-10 at Cin32
Kay, Brendon pass complete to THOMPKINS, K. for 5 yards to the CIN37 (BARRINGTON, Sam), PENALTY CIN personal foul (Bujnoch, Austen) 15 yards to the CIN22.
Cin 1-20 at Cin22
Kay, Brendon pass complete to Chisum, Alex for 8 yards to the CIN30 (DURDEN, Kenneth;CLIETT, Reshard).
Cin 2-12 at Cin30 2nd and 12.
So this is of no help since clearly the play gained more than 5 yards.