If we disregard 100% for a moment, I like "left high and dry."
To explain a bit further: While I believe that "on board" is hard to incorporate here, my issue with "feeling lost" is that it's basically the exact opposite: far removed from any acting agent. If you feel lost, it's first and foremost your own problem if you understand what I'm trying to get at.
Abgeholt, on the other hand, like keep in the loop and left high and dry, all imply--at least to me--that
someone else didn't do their job right and I think that needs to be in there somewhere, especially considering the next statement.
Maybe you could just say something as simple as "not receive a lot of support."
I think this here is a fitting example:
"Often people will feel as though change requires them to go through it alone, that they must be a pioneer and take a risk. But as humans, we want to be part of a winning team or group. Therefore, managers must ensure that their people never feel as though they're working in isolation."
http://www.fortunegroup.com.au/managing-change-in-the-workpl...Also @Tony: Half the time, it could also mean meet someone halfway ("picking them up" after they've started walking).