You have a device that saves information to a USB stick, is that right? Like a scanner or some sort of temperature logger?
To emulate a USB stick would be quite a task, because what you would have to do is pretend that you have a file system, as your device will be opening files, writing to them, and closing them.
It sounds like a lot of work - it might be easier to get another device that actually logs to something like a serial port.
Having said that, it seems on the face of it to be a reasonable request. Just as an example, I have a scanner that writes to a USB stick. It would be handy to have it send files directly to my PC without having to move the USB stick around all the time.
See Make a computer act as a virtual USB device for other equipments as an example of a similar question, with answers suggesting that it might be possible, for example USB-USB cables.
Even if you got it to work, it might be tedious to use. For instance, if your gadget appends to some file on what it thinks is a USB stick you would have to emulate that file system, and then check on your PC if the file has got larger, and thus have new data on it.
Plus possibly the expense (and time) involved in getting this working might be more than just getting another gadget that actually logs via some sort of port, like serial or RS485.
