Hey staingstraight,
Congratulations on your 2 weeks!!
If it were my house and someone came in with alcohol in hand I would have said NO WAY. Your welcome to stay but without the beer! Maybe it was your fiances place to do so since it is his buddy. Would have saved you the uncomfortable silence and ill feelings.
BUT..........its easy to second guess. At the time you were very upset. So next time you'll handle it differently. Have a great weekend!