Who would you ask to be your reference from that company, if any? Would that specific person say that you did indeed suggest this organizational change? That's all that matters, since employers (in Canada or the US) cannot contact someone who did you did not give them permission to contact, without legal recourse.*
*This is an HR perspective; if your industry is small and especially if you live in a smaller community, there will be countless "backdoor" references conducted on you in line at Starbucks or on the football bleachers (much to HR and Legal's chagrin.) Usually, these won't result in combing through your accomplishments with a fine-tooth comb.
As to how to phrase it, "Suggested X and Y which was successfully implemented two months later" would be the simple way.