spec: clarify "Next Pseudonymous IMSI SMS is Lost"

Explicitly state that we send a lost next pseudonymous IMSI again.
diff --git a/docs/imsi-pseudo-spec.adoc b/docs/imsi-pseudo-spec.adoc
index c07281b..ebd499a 100644
--- a/docs/imsi-pseudo-spec.adoc
+++ b/docs/imsi-pseudo-spec.adoc
@@ -386,6 +386,7 @@
 When Insert Subscriber Data Result arrives, a subscriber specific
 Next_Pseudo_IMSI_Timer starts.
 
+[[next-pseudo-imsi-timer-expires]]
 ==== Next_Pseudo_IMSI_Timer Expires
 
 If the subscriber has only one pseudonymous IMSI allocated, and the amount of
@@ -446,7 +447,9 @@
 If the SMS with the next pseudonymous IMSI does not arrive, the SIM/USIM will start
 the next Location Updating Procedure with the old pseudonymous IMSI. Because
 the HLR/HSS has both the old and the new pseudonymous IMSI allocated at this point,
-the subscriber is not locked out of the network.
+the subscriber is not locked out of the network. The HLR/HSS does not deallocate
+the new pseudonymous IMSI that did not arrive, but instead send it again
+(<<next-pseudo-imsi-timer-expires>>).
 
 === Next Pseudonymous IMSI SMS Arrives Out of Order