Clarify behavior of group deletion

ts/models/conversations.ts

@@ -407,6 +407,8 @@ export class ConversationModel extends window.Backbone
     this.unset('tokens');
 
     this.on('change:members change:membersV2', this.fetchContacts);
+    this.on('change:active_at', this.onActiveAtChange);
+
     this.typingRefreshTimer = null;
     this.typingPauseTimer = null;
 
@@ -4416,6 +4418,12 @@ export class ConversationModel extends window.Backbone
     }
   }
 
+  private onActiveAtChange(): void {
+    if (this.get('active_at') && this.get('hiddenFromConversationSearch')) {
+      this.set('hiddenFromConversationSearch', false);
+    }
+  }
+
   async refreshGroupLink(): Promise<void> {
     if (!isGroupV2(this.attributes)) {
       return;
@@ -4846,7 +4854,12 @@ export class ConversationModel extends window.Backbone
         ourAci
       );
     const sharedGroups = ourGroups
-      .filter(c => c.hasMember(ourAci) && c.hasMember(theirAci))
+      .filter(
+        c =>
+          c.hasMember(ourAci) &&
+          c.hasMember(theirAci) &&
+          !c.attributes.hiddenFromConversationSearch
+      )
       .sort(
         (left, right) =>
           (right.get('timestamp') || 0) - (left.get('timestamp') || 0)
@@ -5209,6 +5222,9 @@ export class ConversationModel extends window.Backbone
       active_at: null,
       pendingUniversalTimer: undefined,
     });
+    if (isGroup(this.attributes)) {
+      this.set('hiddenFromConversationSearch', true);
+    }
     await DataWriter.updateConversation(this.attributes);
 
     const ourConversation =