Raynes revealed his disappointment at the way his side were undone by a lapse in concentration - but insisted the team remained confident they could beat the drop.
The 22-year-old told the club's official website: "We just don't know what happened. I don't know how the lad (Wickham) found that much space. I went for the header but couldn't get back quick enough and he seemed to have all the time in the world to put it in the net.
"I think that's the hardest we've worked since I've been here. Everyone's effort was absolutely top class but a schoolboy mistake has cost us.
"We're absolutely devastated about it. We know how hard it is going to be to stay up but with the squad we have we're 100% confident we can get out of it."