I wonder if that had happened at the restaurant before? Probably not otherwise why would they continue to serve the dish so hot. Wow, you were very lucky not to have burns on your face.
"According to the restaurant owner, the incident never happened and escargot does not explode. Still, some in the industry have characterized “escargot explosion” as a “rare but periodic phenomenon” that can be attributed to air bubbles trapped inside the shells during preparation. "
But yours had no shell.
Here's another one:
"It has happened before and apparently this explosion is caused by 'butter and water in the escargot reacting' and 'nothing could be done to prevent this from occurring'.
So, the takeaway is be careful.