When I saw "2a) of a light and loose garment worn at night over a naked body" I thought that that interpretation may have been derived from Mark 14:51-52 itself. I've seen entries that looked like that before. But Thayers refers to two Old Testament verses where the 200 BC Greek Septuagint translation uses the same term and where it's used about linen garments :
Judges 14:12 Then Samson said to them, “Let me pose a riddle to you. If you can correctly solve and explain it to me within the seven days of the feast, then I will give you thirty linen garments and thirty changes of clothing.
Proverbs 31:24 She makes linen garments and sells them,
And supplies sashes for the merchants.
Here we have both the Hebrew and the Koine Greek.
To sum this up, there is no reason to believe that the young man was a resurrected corpse in burial wrappings like Lazarus. The theory is emotionally pleasing in that it produces a new and exciting miracle in the Bible but it doesn't hold water.