Unfortunately SM components are often unmarked, or at least not marked with any recognisable system - you need to find what the component is from the manufacturer of the board, or locate a circuit diagram for it. Both of these are unlikely.
The other way is to draw out the circuit of the board yourself, and work out what the diode is doing, and then find a suitable diode to do that job.
You might be asking yourself why they do things like this. The answer is that they don't expect anyone ever to even attempt to repair a board. Board repair is not something manufacturers are eager to support. Good luck on your quest for the grail.
Thank you all for your input. The only electrical schematics I looked at were at school with a single battery & a light bulb so I'm not qualified to do much.
Dead right, I need to replace that as well. It's a PCB from a DeLonghi Magnifica ESAM 4000/4200 coffee machine. I accidently broke the diode when I took off a heat cover (unsure on technical term).
It says in the ifixit article to replace D1 with a 1N4005. A 1N4006 or 1N4007 would also be suitable, in that case, or the UF versions with the same numbers - whatever you can get.
Yes, fine; just arrange the leads to an appropriate shape so they fit the solder pads on the PCB before you solder it. eg. Cut the to around 10mm & bend to suit.