These were probably dependencies? Did it tell you what they were? if you
have the name, you can go and download the files, then save them to your
flash drive, transfer to your offline PC in your home directory and install
them from a terminal like "dpkg -i package.name" where "package.name" is
the name and extension of the file(s) you are missing.

You can also find what the dependencies are for the program with apt in the
terminal (on your "on line" computer). For example, if you are installing
the gnome network manager that comes with ubuntu, "apt-cache depends
network-manager-gnome" will give you a list of dependencies and recommended
programs to download and install.

There may be an easier way for resolving installations for a pc that is off
line, but I don't know what they may be. Someone else might. You'll
probably want to do some reading if you go the dpkg / apt way in a
terminal.

(If you could get a temporary hard wire connection, that would be best)