Did you get a Critical Hit?
I think I know what you're talking about, Neo Bomber Man, especially when you compared the Ryo situation with Robert's sort of buggy combo, where he does his thing with the kick dance, then a light sweep buffered into his rushing DM. However, I don't think it's that sort of case, although of course I don't know exactly what you did and how you did it with Ryo.
I want to push forward an idea that may help jog your memory. Did you, by any chance, get a Critical Hit during Ryo's 4-hit juggle move? Since Critical Hits are based randomly (for example, Shingo's flying kick has a higher percentage of getting them, but it's never a sure thing,) could that be why you pulled off that combo once but couldn't repeat it? Critical Hits do give you more time to do some sort of follow-up move, so this is the most likely reason for that one-time combo that I could think of.