Hi MonstersU-Terp! I'm sure others will chime in with great advice, but meanwhile I just wanted to say: don't panic. Seems to me you might be worrying too much about this, which is totally understandable and most of us do it all the time - but often the situation is not as bad as we think. Like you said, they don't know you yet - so perhaps they were upset that you took time off without letting your advisor know, which is indeed a mistake but one that you apologized for. Just carry on, work hard, and keep being friendly. Over time they will get to know you and your work ethic. You can't really control what others think of you, so don't worry too much about it - just focus on doing good work and being a good person, and things will find their way. Best of luck!