I kept quiet thinking Trystan would come back, but he hasn’t.
I’m afraid the database is the Feed, so if data is not going into a Feed, it’s not being stored. I think your 4 days of data will be gone forever.
Now, would you believe that nobody tells even us Moderators and major contributors about changes to the system? - somehow we’re expected to read all the documentation every day to find out changes that have been sneaked in. I today or yesterday found one that might have helped prevent your problem - it’s at the top of the file emonhub.conf, which you can get at via Setup → Emonhub.
#######################################################################
####################### emonhub.conf #########################
#######################################################################
### emonHub configuration file, for info see documentation:
### https://github.com/openenergymonitor/emonhub/blob/emon-pi/configuration.md
#######################################################################
####################### emonHub settings #######################
#######################################################################
[hub]
### loglevel must be one of DEBUG, INFO, WARNING, ERROR, and CRITICAL
loglevel = DEBUG
autoconf = 1
### Uncomment this to also send to syslog
# use_syslog = yes
#######################################################################
####################### Interfacers #######################
#######################################################################
if you change autoconf = 1 to autoconf = 0 as I understand it, it should not have created the new set of inputs. I haven’t tried to test this, so I’m wary of suggesting you change it, but again as I understand it, it enables a semi-automatic first configuration, and once you have got that, it should never be needed again. I think it’s this “feature” that caused all the trouble for you.
As for merging your previous data, I know nothing about the post-processing feature. But I will point you towards a very recent post that, or its author, might help you: Python/Pandas Script for API to extract-resample-and replace data
It may well have done exactly that as it restarted from the power failure. I’m not sure of the rules it obeys in this situation.