Job offer/ job rejection

So to keep it short, I applied for a role at a big company in London, went through online tests and assessment centre and the in person interview went very well. Here’s the problem, On Friday I got missed call from there head office (number had no extension) but they left no voicemail, no email. I phoned them back but the receptionist didn’t know who called me and said it’s like there internal recruiter and she will phone me back but she never did. Now the whole Friday and whole weekend I’m stuck wondering is this a rejection, as surely if it this was offer they would have made more of attempt to phone back, Who phones and doesn’t leave a message? Originally I thought it was going to be an offer but as time went on my mind is thinking this can’t be good, surely if I got the job they would have made more of a effort to get in touch? Thoughts?