Hi Almond I totally understand where you're coming from. I also work in a small team - me plus my line manager are full time, then a part-timer who used to do my job before she had her baby (and is now in a different role).
Our department manager had initially said he wanted me to be involved - but have found out through osmosis that my other two colleagues (inc same-level part-timer) and him will be on the interview panel.
I also feel quite anxious about this, not helped by them openly discussing how 'amazing' certain candidates are - one even used the phrase 'I've got a right girl-crush on that one' - when I'm sat in the same office as them.
Every time my input is asked for it's then undermined by same-level colleague so it's as if I don't exist already. Plus, my colleague is being given the opportunity to learn new skills that I am very keen to learn (ie interviewing etc) which I'm jealous as hell about as I have management aspirations before long.
I'm trying to be very mature about it all as I know I won't care as much when I go off, but I am feeling very vulnerable and threatened by it all. I want to know I have a job to come back to - there is talk of if my cover is very good, that they may be taken on permanently, which would put me down the pecking order as they'd been there for the last 8 months whereas I have not.
All I can do is focus on doing things the best I can now, and hope they hire someone who doesn't quite live up to my standards.