really difficult , because it is irreversible when your robber already did transactions you could only know txid (id of transactions),but if have enough authority maybe you can tracked the robber, or ask the online wallet to open the identity use your extra authority, and also if your country legalize bitcoin , you can contact the police. CMIIW
not difficult at all all. i cant still see exactly where my stolen bitcoins have went, up to right now ( i believe they are split up among a bunch of random wallets, they have been spent ALOT of times ). the problem is that i dont know who any of those wallets belong to; they might as well be obscured. this is pretty much the point of bitcoin, at least one of them. being anon, virtually (its not real) while making transactions because addresses are so numerous. the blockchain would be useless if it did not record this.