Seems like confession time - to put your mind at rest
Some months ago I was taking a check ride with an instructor, which took us close to a prohibited zone around a military establishment, at a time of reasonably high alert (terrorist threat etc.). We were both aware of the zone, the instructor discussing with me who it was "down there", as we flew by it.
I was a little bit unsettled, because I had noticed some months earlier that my GPS update from Jeppeson, had shown the zone to be larger than on my chart. I had no trace of a NOTAM indicating the change, and had also recently enquired whether I had the most recent chart - apparently so. I had shown the GPS to another instructor on an earlier occasion and been told - "you can't trust those things". Also, as it was a check ride, my GPS was in the flight bag.
Despite my urge to skirt this zone by a wider margin, the instructor told me to turn "no, no, go straight for that lake". On landing, we were "cordially invited" to contact the military ATC unit who wanted to talk to us, as we had cut through a large segment of the zone (yes it was bigger than on the chart, and my GPS update was correct, and they had tracked us on radar!).
The instructor made the call and he received a right bo!!ocking over the phone. It seems that many infringements of this zone had taken place over the last year, and ATC were getting pretty fed up with it. The matter ended there, apart from a warning that any further infringement would be pursued more seriously.
So I reckon if you only just skimmed it, and you called the ATC Unit to explain, and they didn't seem concerned, then that's the end of the matter, and you don't need to worry about it.
Post Script:
It seems that the zone had been extended by NOTAM before the chart had been produced, and that it was so long ago, that the AIP had been updated and the NOTAM withdrawn. It also seems that no-one in the flying club was aware of it, either. The only way to check was to compare co-ordinates of the zone in the AIP against the chart (and who does that, eh?).
I notice that the wall chart in the flying club now has the zone highlighted in fluorescent pink with its new dimensions.
Horses and stables doors comes to mind!