Front wheel with QR is safe... Not the rest of the bike...
My sister did this some years ago with a Mongoose mountain bike i'd lent to her, stolen on the Lillie Road, outside the Lillie Rec, she came home with a lock and a front wheel with an apology! This was the second time she had not locked one of my bikes correctly and had it stolen, it was also the last time as I realised that I could not keep buying news bikes every few months.
My sister did this some years ago with a Mongoose mountain bike i'd lent to her, stolen on the Lillie Road, outside the Lillie Rec, she came home with a lock and a front wheel with an apology! This was the second time she had not locked one of my bikes correctly and had it stolen, it was also the last time as I realised that I could not keep buying news bikes every few months.