sudo sas3flash -list should list the HBA.
SCALE/CE needs sudo for most useful commands.
I keep forgetting not everyone runs root
Avago Technologies SAS3 Flash Utility
Version 16.00.00.00 (2017.05.02)
Copyright 2008-2017 Avago Technologies. All rights reserved.
No Avago SAS adapters found! Limited Command Set Available!
ERROR: Command Not allowed without an adapter!
ERROR: Couldn't Create Command -list
Exiting Program.
I also ran
sudo lspci | grep -i -E ‘raid|scsi|sata|sas’ and got this output
00:17.0 SATA controller: Intel Corporation 400 Series Chipset Family SATA AHCI Controller
06:00.0 RAID bus controller: Broadcom / LSI MegaRAID SAS-3 3008 [Fury] (rev 02)
This card is installed in the server
RAID Controller Card, LSI SAS3008 9300-8i PCIe 3.0 12Gbps HBA Host Bus Adapter in IT Mode, 8-Port Low Profile Storage Expansion Card for ZFS FreeNAS and unRAID Servers
Interesting… so it is detected in the pcie slot at the very least. I’m wondering if it needs to be reflashed in uefi… Haven’t done that on a 3008, so can’t advise…
I’ll see what the internet says about the process and get on it.
Well at very worst, it is already non-functional, so hopefully it just needs firmware reflashed & then you can save some money on a replacement. Everything is already too expensive as is 
Maybe this is helpful
If it turns out I do replace the raid card in IT mode, I’m open to recommendations… anyone have a favourite card the want to promote?
sas9211-8i is old af, runs hotter, but is pretty damn cheap & readily available second hand (in my area). I’ve seen these from $30-$50 CAD, with cables.
Otherwise, the 9300 card you have is the next step up & is a perfectly acceptable option.
Other three-ish, would be to reach out to
https://www.ebay.com/str/theartofserver
Reputable seller; dude will prolly even give a recommendation.
Unless this was loaded with IT firmware, this is a Hardware RAID card unsuitable for use with ZFS. Even if drives are made into individual RAID-0 LUNs. Some “MegaRAID” cards are difficult, (or impossible), to load IT firmware.
The tools listed, sas3flash and sas2flash, are not suitable for MegaRAID cards. They are for the HBA & lightweight RAID cards. Which if in IR mode, Integrated RAID, can be reloaded with different firmware for IT, Integrated Target mode.
It is somewhat common for hardware RAID cards to cause problems with ZFS. Thus it is highly recommended to avoid such for home and small business NAS use, (when using ZFS).
It is possible that the drives are fine, depending on how they were configured on the MegaRAID card.
Further, it may be possible that the MegaRAID card simply lost it’s configuration during the power down to replace the boot drive mirror. So it may be possible to go into the appropriate utility, (which is NOT supplied with TrueNAS), or use the BIOS based utility, to restore the drive’s configuration. Note that this could be potentially dangerous to your data.
If this truly is a Hardware RAID recovery from a MegaRAID card, then this is quite complex in that care has to be taken in regards to drive / data safety. In essence, one wrong move and one of the affected pools may be destroyed beyond reasonable recovery.
Sorry if I am sounding alarmist, but the above is my understanding.