According to answer of Matthew Scharley here: http://gaming.stackexchange.com/a/81900

things won't move through unloaded pipes either so you won't get your materials till you go near the pipeline.

and comment of Jonathan Drain here: How many chunks do I need to keep loaded to keep quarries working in Buildcraft?

Everything fell out of the pipe at the point where it reached the unloaded segment.

I tried to test it and I think that the items in the pipes in the chunks that were unloaded will just stop. They will not disappear. For new items heading through pipes into unloaded chunks, I think it is very likely that everything fell out of the pipe at the point where it reached the unloaded segment, although I do not have enough time to test it and strong evidence to prove it.

According to answer of Matthew Scharley here: https://gaming.stackexchange.com/a/81900

things won't move through unloaded pipes either so you won't get your materials till you go near the pipeline.

and comment of Jonathan Drain here: How many chunks do I need to keep loaded to keep quarries working in Buildcraft?

Everything fell out of the pipe at the point where it reached the unloaded segment.

I tried to test it and I think that the items in the pipes in the chunks that were unloaded will just stop. They will not disappear. For new items heading through pipes into unloaded chunks, I think it is very likely that everything fell out of the pipe at the point where it reached the unloaded segment, although I do not have enough time to test it and strong evidence to prove it.