If you were to put your hydrometer into a 100% ethanol you would actually get a reading of 0.785. Remember we're using a hydro-meter (water meter). Pure water is by default set to a density of 1.000. However, since Ethanol is much less dense than water, and will even float on it (try dropping an icecube into ethanol), your hydrometer is effectively "floating" - giving you a reading <1.000. It follows that if you made a solution with 50% ethanol (100 proof) and 50% water, you'd get a measurement 0.89; and 25%/75% would yield 0.9463.
So, how would this work with beer? It is nearly always the case that beer will finish with an FG higher than 1.000. This is because most beer contains lots of non-fermentable sugars (malti-goodness) in addition to proteins, fatty acids, etc. HOWEVER, if you were to create a very high gravity (>1.09) that consisted of mostly fermentable simple sugars (i.e. mash at 140 for two hours), and a attenuative yeast strain, the resulting beer would end up being high in alcohol, but also have a relatively low FG based on sugars, protein, and fatty acids. Add back that you've also created 10-12% ethanol and bang - your FG is below 1.00.
This is exactly what happens if you make a 12-14% wine that is particularly dry (i.e. low residual sugar). These wines should finish below 1.000.
All that said - your OG was like 1.05, so even if completely fermentable, you would have created a high enough concentration of alcohol to dip the hydrometer below 1.000.
Make sense?
Pete