I'm not sure how Apple has people convinced they need ECC. It's practically worthless outside of very specific workloads. A workstation user does not fill several gigabytes of RAM with terse important data, query it millions of times/day, and do so 24/7 all year long.
I've also had memory issues on non-ECC machines, it's a lot harder to diagnose and much more frustrating. ECC memory should be standard in modern machines IMO.
And didn't keep a backup. Most serious software will make incremental copies to avoid that problem too.
Seriously, hardware failures are just as likely.
ECC is useful, but isn't worth it for the price unless you actually can't be fault tolerant in any way.
Software is fault tolerant. Small memory failures can be trivially tolerated.
ECC simply isn't worth the cost, especially for workstations.
Most software is not at all fault tolerant in this respect. It just crashes. Fortunately, most users are somewhat fault-tolerant.
The chances of memory failure ruining data are extremely slim; lower than for hardware failure. If you care about your data, back it up.
As for the source of the error, we can only speculate but the possibility of a flipped bit is higher than you think.
Try running memtest86 on a PC without ECC for a week. You will be surprised at the results. I’ve seen perhaps 3 or 4 failures of this in new hardware. DRAM is not perfect.
Also SSDs scare me more. MLC disks have so many states stored in a capacitor that is trusted not to leak over the lifetime of the device. All it takes is a few electrons to go walkies and it’s game over.
And then there’s the same problem with MLC SSDs which are just arrays of capacitors encoding that state as different charge potentials. As a former EE, capacitors leak regardless of implementation.