I think vinegar would make it too... Vinegary. How about if you zested the half lemon, cut off the pith, and pulverized it and the zest in the food processor with the chick peas, etc.?. You'd get more intense lemon flavor without the vinegar. (Just my opinion)

In the "what it is worth" department, I frequently make hummus with balsamic vinegar instead of lemon. It is quite wonderful and not the least bit "vinegary".

Also, you can garnish with sumac to boost the citrus flavor a little.

...should it happen again in the future, that is. :)

Yes you can! Matter of fact, I was just looking for an answer to this earlier, before making hummus, and I thought "oh what the hell, I'll try it and see how it goes." And I'm glad it turned out great. I used balsamic vinegar as a substitute. If anything, I think it went slightly better this time.