Apparently there are different holding lists. The main
differentiation, if true, being the MINDEF "inactive" one (for the
retired & the downgraded -- both no more under SAF strength,
mah), the combat "standby" ones (all the combat DIVs &
formations have their own holding lists), the TRADOC "paper" one
(for those non-ops ready but arrowed) & the NSPC "limbo" one
(for NSF disruptees or NSmen working/studying overseas).
Did I guess correctly in your case? ~lol~ If so, the good news is
your aptitude may be too obsolete or lapsed when available for
call-up again; the bad news being you may still be posted
nonetheless, starting anew in, say, your 30s with a newly-ORD unit
when your peers are winding down their cycle. Better cross your
fingers ....
I also believe the SAF can switch the lobo reservists between the
lists anytime, without necessarily informing them.