I was working on something in the beginning of my piece (where I added bars etc.) when I went to look on the piece I had already fully written. Somehow the notes (and only the notes, not the dynamics, playing techniques etc.) has moved 3 and 3/4 of a measure away from where it was… Imgur: The magic of the Internet
Please help me, I am desperate. I have worked so hard on this for over a month! 
You might have activated Insert Mode at some point - by inadvertently pressing the key “I”. In this mode music gets shifted or deleted - but other things like dynamics don’t.
Luckily you can use the same mode again to fix the situation. Press “I” and add or delete the bars your music is offset. Please be aware that different voices per staff get treated independently.
This has happened to me as well. It would be useful for dynamics to stay attached to their notes when using Insert mode - is that possible?
In the meantime, if you want to move your dynamics without adding/deleting bars, you can select Edit->Filter->All Dynamics, and then move your dynamics with the keyboard shortcut (alt-arrow on Mac). Your dynamics will move backward or forward by the amount shown in the rhythmic grid (bottom left corner of your screen).
If you attach a dynamic to a specific voice, rather than to the general rhythmic position, it will move along with that voice. Add the modifier Alt as you press Enter in the popover.
You learn something every day! Thanks!
Yes, that is useful to know! But I’m still wondering: if a staff only has one voice, it would be great to have the dynamics automatically attach to that voice. I don’t know if that would be too much of a headache, though, once a user starts adding/changing voices, etc.