It could be MANY things. Maybe it was only 'perfect' to you.... I'll tell you what I would do at some point in all this.
Pricing is why I never liked commercial.... it was already so low there wasn't much profit and then guys come in and lower the price even more. Atleast with residential the potential customers know that cheap cleaning ain't the best cleaning and most of the time don't hire the $10 an hour cleaners because they know it won't last long.
Anyway.... I'm just throwing thoughts out there.... it could be one of these or it could be 1 of a million more. But.... if you think your job was perfect and you are 100% sure they loved your work and wouldn't have anyone else come work for them.... you are what was once known as a green horn. Now it could be true... your work might have been AMAZING! But lots of times even if your work sucked or even if you thought it was amazing but they thought it sucked, they will tell you it looked great because it's human nature to not want to hurt your feelings.
It could be that what you did is lasting longer than the other floor guys because you knew what you was doing.... so it might be every 6 months before they want you back.
It could be because they have been busy and just haven't called.
They might have lost your number.
Someone else might have contacted them and gave them an even lower price.
Or one of the other million things that could have happened. What I would have done when the job was completed, ask if you can give them a call in 30 days to set up their buffing (or what ever needed done). Now that gives you a time line to call.... see, they might be wondering why YOU never called..... damn, I guess that was a fly-by-night guy, too bad because he was really good. But since you didn't do that, give them a call and just say that you are wondering if they would like for you to come in and (do what ever it is that needs done... buff/what ever...). If they set up a time, then do what I told you above once the job is complete. That way you have a time line. If they say not right now.... it could be a million things again.... maybe it was only perfect to YOU. Either way, ask when you can call back. If they say call back in 2 weeks then call back in 2 weeks. If they seem flaky about it..... you know what the deal is.