I don't think this has a single answer: The amount of alcohol would depend on the alcohol content of the soaking liquor or liqueur, soaking time, temperature of chocolate, and how thick the strawberry was.
I suspect uncut strawberries would take at least several days to fully absorb alcohol and reach equilibrium, but the surface should take up alcohol fairly quickly. If they are cut up, exposing the more porous interior, I imagine an overnight soak would be sufficient to reach maximum alcohol content. The enormous, bloated mutant strawberries you sometimes see at stores could take considerably longer than others to absorb their maximum alcohol.
Alcohol is much more volatile than water, so the immersion in warm, melted chocolate would remove some alcohol, but once the chocolate cools, it should trap any remaining content.
The flavor of alcohol is easily masked by other flavors at under 20% content; this could explain why your friend didn't taste it, but you did. It's quite possible the strawberries packed a sobriety-busting punch, but it was disguised by the chocolate and fruit tastes.
Best Answer
The optimum amount of time depends on what you want to achieve:
Another element to consider is the fruit-to-alcohol ratio:
The less alcohol is present, the less solvent is there to draw the aromatics from the fruit. This means, for flavoured fruit, barely covering them is enough while to "fully" extract the fruit you might go for a liquid level that is up to twice as high as the fruit in your container.
For longer soaking times, the alcohol content is crucial. I learned that everything over 40 %vol (= 80 proof) should be fine to keep the fruit from spoiling during extraction even at room temperature. Use higher proof if using a higher (soft) fruit content w/o sugar if you plan on soaking long term. But always use unblemished fruit. Not only to ensure the shelf life of your product, but also because even slight traces of an "off" taste can be amplified and and spoil your whole batch.
The addition of sugar is optional, keep in mind that your fruit bring sugar, too. Sugar may speed up the extraction process a bit because it helps breaking down the cells. This may or may not be desired. Also, sugar acts as a preservative, so it's recommended for lower-alcohol concoctions.
If you like the results of your pear experiment, you might consider setting up a "Rumtopf" as an ongoing project for summer:
Starting in June with strawberries, layer about 1/2 to 1 pound of fruit with 1/2 the weight of sugar in a large jar, cover with rum (preferably 110 proof) and weigh down with a plate. Rum should be always 1 inch above fruit level. Close the pot and store in a dark space if the pot is not opaque. During summer, top up with more fruit and sugar whenever they are ripe (cheries, peaches, raspberries, pears, plum...). Start serving 6 weeks after the addition of the last fruits.