PC1 & PC2 were setup for sharing/syncing a folder.
1. I removed an internal HDD which had the shared folder from PC1.
2. I booted up PC1 again, Sync showed that the shared folder was no longer there, which was correct.
3. I booted up PC2, i saw in the history of Sync on PC2 that it had deleted the files in the root of the shared folder after booting.
Lucky for me i still had the files on the HDD which i took out of PC1.
I'm sorry i do not have log files, because i immediately removed Sync from PC1 after seeing that Sync was deleting files on PC2.