Yes, I was able to recover this modem using DWLWin. 
The process was not nearly as easy as it could have been, given better documentation and access to software resources, so I’ll do Sierra’s job and add instructions here:
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Download and Install DWLWin; requires login to SiWi developer resources (unnecessary but straightforward). The user manual is rubbish for ad-hoc usage, detailing loads of COM automation but not the actual physical usage.
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Setup switch on BOOT pin of modem, in the SL6087 case its direct to the 1.8V pin
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Get appropriate .wpk package for the firmware version. Once again, SiWi stand in the way by not publishing these conveniently. You have to do a request through the distributor, which is a massive waste of time. DWLWin only works on .wpK packages, not .dwl files, which is the only useful comment in the manual.
The package will include all firmware and bootloader as required - its quite neatly automated. -
Start DWLWin and point it to your package(s); they should appear in the UI and you can select the one you want. Set for autodetect of module type. Press the START button
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While its trying to detect the module, ensure the BOOT switch is on and reset (or power up) the modem. It will be found by the DWLWin software and some fairly straightforward questions will be asked on the way to reflashing your modem.
Works really well when you have what you need and know what to do. 8)